A few readers may remember the novelty ads appearing in magazines to X-ray Specs, an item that were advertised as being able to allow you to "see the bones in your hand, see through clothes!"
Some versions of the advertisement featured an illustration of a young man using the X-Ray Specs to examine the bones in his hand while a voluptuous woman stood in the background. In case anyone is wondering...they didn’t work.
After mailing in a dollar plus 25 cents for shipping and waiting 6-8 weeks for delivery, you got a large pair of “glasses” with plastic frames and white cardboard "lenses" printed with concentric red circles and emblazoned with "X-RAY VISION".
The lenses consist of two layers of cardboard with a small hole about a quarter-inch in diameter through which objects were viewed. There was a feather is embedded between the layers of each lens. The feathers diffracted light causing the user to receive two slightly offset images.
For instance, if viewing a pencil, one would see two offset images of the pencil. Where the images overlap, a darker image is obtained, giving the illusion that one is seeing the graphite embedded within the body of the pencil.
The principle behind the illusion was first patented in 1906 by George W. Macdonald. In 1909 Fred J. Wiedenbeck patented a tube employing the same principle. X-Ray Specs were improved by Harold von Braunhut, also the inventor of Amazing Sea-Monkeys.
There was even a movie inspired by X-ray Specs released in 1963, X: The Man with X-Ray Eyes starring Ray Milland; it was a low budget film about the experiences of a doctor who acquired x-ray vision by testing vision enhancing eye drops on himself.