Thomas Edison had a tatoo of 5 dots (like on a dice) on his left forearm

According to a 1911 policy with the Mutual Life Insurance Company of New York, Edison had five dots tattooed on his left forearm. No one knew what the dots meant.

Interestingly, Edison was credited for inventing the basic tattoo machine. In 1876, he patented the Stencil-Pens, an engraving device that many years later was modified by Samuel O’Reilly to make the world’s first tattoo machine.

Though it would’ve been a neat thing, there was simply no evidence that Edison used his invention to give himself a tattoo.

http://www.neatorama.com/2008/02/11/10-fascinating-facts-about-edison/