This link has been around for a few years now and quotes Mas. Oyama's autobiography where the founder of the Kyokushinkai style of karate apparently claims that he lost a fight to an elderly tai chi master.
What I would like to know is if anybody here can verify this story. The only autobiography of Oyama that I know of is in Japanese. Anyway, here is the link:
www.crane.50megs.com/index6j.htm