The above photos show an interesting looking model circa 1920 demonstrating the usage of a violet ray machine, which was a personal electrotherapy device first invented by Nikola Tesla around 1890. Tesla was way ahead of his time, and some of his electrical applications were simply amazing. For instance, he successfully generated wireless power—i.e., he lit phosphorescent lamps by sending electricity through the air. Think about that next time you trip over one of the twenty power cords you have snaking around your place. Of course, genius occasionally comes wrapped in a bit of lunacy, so in the interests of full disclosure we should probably note that Tesla also spent many years trying to build a teleforce weapon, which he claimed would “bring down a fleet of 10,000 enemy airplanes at a distance of 200 miles from a defending nation’s border and cause armies to drop dead in their tracks.”

Tesla’s violet ray device became a major fad during the Great Depression. The contraption consisted of a portable box encasing a discharge coil that produced a high frequency, ozone-generating electrical current. That current was channeled into a bakelite-handled, glass-tipped wand, the business end of which was applied to the recipient’s skin. One company that manufactured these devices was called Renulife, and their pitch went like this: Electricity from your light socket is transformed into health and beauty-giving Violet Ray—powerfully effective, yet gentle, soothing, perfectly safe. Voltage is raised from ordinary lighting current to thousands of volts, giving tremendous penetrative force. The irresistible revitalizing powers of Renulife Violet Ray are carried at once to every nerve, cell, fibre and part of the body.

Violet rays were touted as the cure for a long list of ailments, including fatigue, congestion, rheumatism, hemorrhoids, catarrh, brain fog, aging, and so forth, but by the 1950s Tesla’s device had fallen out of usage in the U.S. While it would be easy to dismiss violet rays as quackery, something physical was clearly happening. Consider this: the Chicago Police Department used a violet ray device to torture suspects between 1973 and 1984. Also, it’s worth noting that similar devices are still used today, most notably the High Frequency aesthetic machine you find in beauty salons, and the violet wand, used in BDSM. And modern medical research has shown that electricity can speed the healing of wounds, slow muscle atrophy, and modify brain impulses. So give Tesla his props—looks like he was right yet again. Good thing he never wrote down how his teleforce weapon worked.