John Napier.

[akka]

The 16th Centuary mathematician John Napier was a clever chap, as one would expect. Once, he got his black **** out in the dark, and then sacked the servant with the clean palm, Why?

[gen2]

The story is told here and on many other sites if you search with Google

"According to another story, Napier believed that one of his servants was stealing some of his belongings. He announced that his black rooster would identify the transgressor. The servants were ordered into a dark room, where each was asked to pat the rooster on its back. Unknown to the servants, Napier had coated the bird with a layer of lampblack. On leaving the room, each servant was asked to show his hands; the guilty servant, fearing to touch the rooster, turned out to have clean hands, thus betraying his guilt."