The Osculum Infame is an integral part of the Witches' Sabbats of historical legend. At each Sabbat, the Devil, who generally appeared as a Goat, would take a roll call of sorts, and record the names of those in attendance into his Red Book. Following this task, each witch present was expected to then offer homage to her master through what is known as the Osculum Infame.
Seen as the ultimate act of submission and degradation, the witch was expected to either walk or crawl backwards toward the devil (or presiding demon), turn, bow, then kiss him directly on the anus, which was often described as being "cold as ice."
Some witches claimed that they were not actually kissing his anus, but rather, there was a second face in place of the anus. In any event, the act was seen as the total embodiment of the witch's relationship with the Devil. This was seen as an unnatural act, and the epitome of all that was unclean and degrading. However it was seen, this photograph and accompanying description of the ritual has led to plenty of interesting discussion and jokes on various message boards concerning "demon salad tossing," hehehe.
A new witch was not accepted until she performed this act, and the practice was reported in each and every confession that was tortured out of suspected witches during the Inquisition. Following the ritual, the Sabbat continued with a banquet, dancing, orgies, etc.