There's not a person in the world who has looked at American comic books from the 50's through the 80's and isn't familiar with a device called X-Ray Specs. There would always be a half-page ad from some novelty company offering items like onion gum, joy buzzers, whoopie cushions, and the mysterious magical spectacles.
They promised the ability to see the bones in your hand, and hinted that you just might be able to see through curvaceous young ladies' clothing, as well.
Talk about something that grabbed the attention of a young male!
I never knew of a single friend of mine who actually ordered a pair, though. We just never could justify spending candy bar money on something that, while looking very intriguing, also carried with it that curious phrase "a hilarious optical illusion." That phrase seemed to imply that it didn't really use x-rays to allow a peek under young ladies' dresses! Come on, for a dollar, this thing better be the real deal!
In researching X-Ray Specs, I found the explanation on how they work here. Wow, talk about an unexciting revelation.
However, if you want to go ahead and spring for something you may never have bought as a child, you can order a pair from Stupid.com. Inflation being what it is, though, they're up to three bucks.