Taken in the spring of 1894, and originally published as part of an article by T.C. Martin called “Tesla’s Oscillator and Other Inventions” that appeared in the Century Magazine (Vol. 49, issue 6, April 1895, p. 930).

You can see the same picture in the online archive of the Century Magazine as well as read the article it illustrated. Here is the original caption from the magazine:

Fig. 13 Similar experiment, the high-tension current being passed through the body before it brings the lamps to incandescence. The loop is held over the resonating coil by Mr. Clemens (Mark Twain). (From a flash-light photograph)

This post is for a friend whom I shall now call Doctor.