X-Ray Spex (ca. 1990s)

This is a 1990s version of the famous X-ray specs that have appeared in the advertisement sections of comic books at least since the 1950s.

The trick is that there are feathers sandwiched between the two sheets of cardboard from which the glasses have be cut out. When you look through the two 1/4" holes, you are actually looking through the feathers. The veins of the feathers are so close together that they diffract visible light and create the quasi-impression of an X-ray.

Various versions of this "trick" have been around since 1900 or so.