A Reward Check From Donald Knuth

The other day I went to my pigeon-hole to collect my snail mail, and I had a letter from Donald E. Knuth, Professor Emeritus of the Art of Computer Programming! Inside, there was a check for a correction I sent him some months ago. In fact, it was not really a correction; it was more like a comment. And it was so obvious (he even said that) that he just sent $0.