The May 2024 issue of IEEE Spectrum is here!

Close bar

The Electric Purple Snake-Oil Machine

The violet ray machine’s Tesla coil could cure almost anything—supposedly

6 min read

An antique medical apparatus consisting of a black wand, various glass tools to plug into the wand, and a power cord.

The violet ray machine became a popular electrotherapy in the first half of the 20th century.

Historical Medical Library/College of Physicians of Philadelphia

The violet ray machine has an awesome name that conjures up images of cartoon supervillains taking out Gotham, but its actual history is even odder—and it includes a superhero, not a villain.

The technology underpinning the machine begins with none other than Nikola Tesla and his eponymous coil. After Tesla and others made some refinements to the device, an influential clairvoyant named Edgar Cayce popularized violet ray machines for treating just about every kind of ailment—rheumatism and nervous conditions, acne and baldness, gonorrhea and prostate troubles, brain fog and writer’s cramp. Even Wonder Woman had her own health-restoring Purple Ray device. During the first half of the 20th century, a number of companies manufactured and sold the machines, which became ubiquitous for a time. And yet the scientific basis for the healing effects of violet rays was scant. So what accounted for their popularity?

The cutting-edge tech of the violet ray machine

Violet ray machines employ a Tesla coil, also known as a resonance transformer, to produce a high-frequency, low-current beam, which is then applied to the skin. Nikola Tesla kicked off this line of invention after traveling to Paris during the summer of 1889 to attend the Exposition Universelle. There he learned of Heinrich Hertz’s electromagnetic discoveries. Intrigued, Tesla returned to New York City to run some experiments of his own. The result was the Tesla coil, which he envisioned being used for wireless lighting and power. In April 1891, he applied for a U.S. patent for a “System of Electric Lighting,” which he received two months later. It would be the first in a series of related patents that spanned more than a decade.

In May of that year, Tesla unveiled his wondrous invention to members of the American Institute of Electrical Engineers, during a lecture on his “Experiments with Alternate Currents of Very High Frequency and Their Application to Methods of Artificial Illumination.” He continued to test different circuit configurations and patented some (but not all) of his improvements, such as a “Means for Generating Electric Currents,” U.S. Patent No. 514,168. After more years of tinkering, Tesla perfected his resonance transformer and was granted U.S. Patent No. 1,119,732 for an “Apparatus for Transmitting Electrical Energy” on 1 December 1914.

An old black and white photo showing a man sitting next to a large electrical apparatus that is emitting sparks.Nikola Tesla envisioned his eponymous coil being used for wireless lighting and power. It was also at the heart of the violet ray machine. Stocktrek Images/Getty Images

Tesla promoted the medical use of the electromagnetic spectrum, suggesting to physicians that different voltages and currents could be used to treat a variety of conditions. His endorsement came at a time when trained doctors as well as shrewd hucksters were already experimenting with electrotherapy and ultraviolet light to help patients or to make a buck, depending on your perspective.

The market was perfectly primed for the violet ray machine, in other words. Tesla himself never commercialized a medical device based around his coil, but others did. The French physician and electrophysiologist Jacques-Arsène d’Arsonval modified Tesla’s design to make the device safer for human use. It was further improved by another French doctor and electrotherapy researcher, Paul Marie Oudin. In 1893, Oudin crafted the first working prototype of what eventually became the violet ray machine. Four years later, Frederick Strong developed an American version.

An influential clairvoyant named Edgar Cayce popularized violet ray machines for treating just about every kind of ailment—rheumatism and nervous conditions, acne and baldness, gonorrhea and prostate troubles, brain fog and writer’s cramp.

Another charismatic individual gets credit for popularizing the device: the psychic Edgar Cayce. As a young adult, Cayce reportedly lost his voice for over a year. No doctor could cure him, and in desperation he underwent hypnosis. He not only regained the ability to speak, he also began suggesting medical advice and homeopathic remedies. Cayce, who claimed to have had visions from childhood, became a professional clairvoyant, and for the next 40 years he dispensed his wisdom through psychic readings. Out of more than 14,000 recorded readings, Cayce mentioned the violet ray machine almost 900 times. In case you doubt his status as an influencer, Cayce counted Thomas Edison, composer George Gershwin, and U.S. president Woodrow Wilson among his clients.

Was there nothing the violet ray machine couldn’t cure?

The popularity of violet ray machines exploded after 1915, once all of the components for a portable device could be easily manufactured. They could be plugged into a lamp or wall socket or wired to a battery—remember that most homes and businesses in the early 20th century were not yet electrified, and so most manufacturers offered both alternating and direct current options. The machine’s handheld wand consisted of a Tesla coil wrapped in an insulating material, such as Bakelite. The coil produced 1 to 2 kilovolts, which charged a condenser, and then discharged at a rate between 4 to 10 kilohertz when passed over the skin. A voltage selector controlled the intensity of the spark, creating anything from a mild sensation to something quite intense. This video shows the sparks coming from an antique machine:

Glass electrodes—partially evacuated glass tubes known as Geissler tubes—could be inserted into the wand. These came in different shapes depending on their intended use. For example, a rake-shaped attachment worked to massage the scalp, while a narrow tube could be inserted into the mouth, nose, or another orifice. The high voltage ionized the gas within the glass tube, creating the purple glow that gave the device its name.

Numerous manufacturers sprang up to produce the portable machines, including Detroit’s Renulife Electric Co. Founded by inventor James Henry Eastman in 1917, Renulife sold different models for different uses. According to company literature, Model M was its most popular general-purpose product, while Model D was for dentistry, and the tricked-out Model R [pictured at top] had finer regulation of current and a built-in ozone generator to help with head and lung congestion.

In 1917, editors at the Journal of the American Medical Association reported that a violet ray generator certainly couldn’t treat “practically every ailment known to mankind,” as one manufacturer had claimed.

Instructions for the violet ray machines manufactured by Charles A. Branston Ltd. contain an alphabetical list of disorders that could be treated, from abscess to writer’s cramp, with dozens of other ailments in between. Like the Renulife products, the Branston machines also came in different flavors. The Branston machine’s high-frequency mode had germicidal effects and purportedly could be used to cure infections as well as relieve pain. Sinusoidal mode was used to gently massage away nervousness and paralysis. Ozone mode was for inhaling, to treat lung disorders. The Branston devices ranged in price from US $30 for the Model 5B (high-frequency mode only) to $100 for the Model 29 (which had all three modes).

A page from a pamphlet showing the potential uses of an electrotherapeutic machine. The violet ray machines made by Charles A. Branston Ltd. had different modes for treating a wide variety of ailments.Historical Medical Library/College of Physicians of Philadelphia

During the first half of the 20th century, manufacturers marketed the machines to doctors and consumers alike. By the time Wonder Woman debuted in her own comic book in June 1942, the violet ray machine was a well-known household technology. So it wasn’t too surprising that the superhero had a machine of her own.

In the very first issue, Wonder Woman’s future love interest, Steve Trevor, is grievously injured in a plane crash. Seeking to cure his wounds, Diana works tirelessly for five days to complete her Purple Ray machine—but she’s too late. Trevor has died. Undeterred, Diana bathes her patient in the glowing light of the machine. The result might have embarrassed even the admen who wrote the promotional copy for Branston’s products: Wonder Woman’s Purple Ray brings Trevor back to life.

Science frowns on the violet ray machine

Despite their popularity, the machines didn’t fare quite as well within the medical establishment. In 1917, editors at the Journal of the American Medical Association reported that a violet ray generator certainly couldn’t treat “practically every ailment known to mankind,” as one manufacturer had claimed. Although the devices emitted a violet color, they were not in fact emitting ultraviolet light, or at least not in amounts that would be beneficial. In 1951, a Maryland district court ruled against a company named Master Appliances in a libel suit. The charge was misbranding, and the court found that the device was not an effective treatment nor capable of producing the claimed results. At the time, Master Appliances was one of the last manufacturers of violet ray machines in the United States, and the ruling effectively ended production in this country.

And yet you can still buy violet ray machines today—both the antique variety and its modern equivalent. Today’s units are mainly marketed to aestheticians or sold for home use, and some dermatologists are not ready to categorically dismiss their benefits. Although they probably won’t cure indigestion or gray hair, the high frequency can dry out the skin and ozone does kill bacteria, so the machines may help treat acne and other skin conditions. Plus, there’s the placebo effect. As with all consumer electronics for which outrageous claims are made, let the buyer beware.

Part of a continuing serieslooking at photographs of historical artifacts that embrace the boundless potential of technology.

An abridged version of this article appears in the October 2022 print issue.

The Conversation (3)
Thomas Valone
Thomas Valone16 Nov, 2022

Subject:  Complaint regarding "Past Forward" by Allison Marsh, October 2022


As a longtime member of IEEE, who is applying for Senior Membership, I value the Spectrum content and quality every month. The most important quality to me is the scientific validity and in-depth research that is most often combined skillfully in every article.

 However, after decades of reading IEEE Spectrum, I have never seen a biased review bordering on prejudice with little or no updated, scientific research included, except this past month on p. 56 of the October 2022 issue. Giving Allison the benefit of the doubt, I visited the pastforward-oct2022 webpage and read all of the extra copy including a video or two as well, some of which contradict her strong “snake oil” and “quasi-medical” opinion by indicating specific health benefits they know about from personal experience.

 Interestingly, Spectrum also seems to side with her slant by linking IEEE 1999 reprint of Nikola Tesla’s “medical use” article to a pay-to-view Proceedings of IEEE website that stops most IEEE members from viewing Tesla’s insightful and eloquent “High Frequency Oscillators for Electro-therapeutic and Other Purposes” 1898 article, unless they happen to subscribe to that additional publication in their membership package, when the original article (with graphics) actually is available for FREE on (

Normally, it is nice to see some historical information about present day inventions, comparing the two, but the denigrating “electric purple snake-oil machine” title on page 56 does not set well with anyone familiar with the present day Tesla coil devices and their bioelectromagnetic and electrotherapeutic applications. I have lectured widely on the subject of high voltage electrotherapy, which is also supported by a plethora of medical journal studies, some of which also use Tesla coil devices. I am also the author of Bioelectromagnetic Healing: A Rationale for its Use, first published in 2003 and now in its 14th edition, available in paperback, Kindle, audiobook, and audio CD. The two main points of my book and slideshow are 1) “tissues are condensers” as Nikola Tesla stated, which leads to my modern day therapeutic advantage also on a firm foundation: “electrons are antioxidants” and 2) the transmembrane potential (TMP) of every bodily cell, which is about 100 kV/cm in healthy people, can be charged up in debilitated people with a brief proximity to a source of high voltage (DC or AC) with tangible results. The simple explanation from the standard biophysics textbooks (which may be beyond Allison’s reach) is that the body stores energy in two ways: a) chemical gradients, and b) electrical gradients, so charging the cell membrane’s lipid bilayer with an exogenous electrical gradient of sufficient magnitude can have lasting effects for metabolic energy levels.

 Our nonprofit, charitable research organization also has experimental Tesla coil devices that many clinicians, chiropractors, as well as medical doctors are presently using, thanks possibly to my book and insistence on scientific references and historical use integrity. One of the interesting applications of the present day higher voltage version of violet ray devices, confirmed by our clients, is significantly reversing neuropathy. Journal support is found citing nerve regeneration by applied high voltage ( ). Relieving pain and inflammation is another very common benefit, actually mentioned in one of Allison’s posted videos on your pastforward-oct2022 website concerning back pain, thus contradicting her repeated theme of useless snake oil.

It should also be mentioned that Scientific American has done a more useful job of informing the public in their cover story about the modern electrotherapeutic developments "Electric Cures: Bioelectronic medicine could create an 'off switch' for arthritis, diabetes, even cancer" in the March 2015 issue, .

 Of course, when the Flexner Report came out in 1910 boasting “analytical reasoning” with AMA and FDA support, funding was cut for universities and hospitals involved in such alternative health and medical subjects, which can be partially blamed on widespread, uncontrolled advertising abuse with exaggerated health claims at that time. Allison clearly concentrates on this latter problem exclusively. Thus the newly emerging electrotherapy baby, only available with AC power delivery after 1895, was thrown out with the bath water and the ramifications are still felt today in an electrotherapeutically deprived medical community in this country, significantly more than with overseas.

 I can also point to the immense 800-page Medical Electricity textbook published in 1916 by Sinclair Tousey, M.D. with over 200 pages devoted to his personal research with his patients using high voltage Tesla coil electrotherapy, which we were fortunate to borrow for a month to have volunteers scan for us and make available for free to customers on a CD.

 For more information on this neglected medical and scientific topic, one of my articles is also online: Please consider an updated equal time counterpoint such as a medically technical article to balance out the one-sided personal bias throughout historian Allison Marsh’s storyline.


 Thomas Valone, PhD, PE, IEEE #40182979


Integrity Research Institute

5020 Sunnyside Avenue, Suite 209

Beltsville MD 20705

301-220-0440, 800-295-7674



Thomas Valone
Thomas Valone16 Nov, 2022

1 Reply