Also pick up a copy of the 2010 Farmer's Almanac. I got one for Christmas, for whatever reason, and there's a nice little piece in it. However, be warned, that it depicts the torture as a means to cause death.
Oddly enough when I was in college I found a few obscure references in psycology texts. Dr's would post their interesting cases in these. You could probably still find them in larger libraries. There was also a book called "The Sex Life of the Foot and Shoe" that had tickling references. One...