I believe the rule was one empty handed monk could handle 10 AVERAGE men, and with his cudgel 100. apparently we all suck today. i believe this was tested in the 70's and it came out about 10 since thats all that can get to one man without being in each others way. Even 5 on one is a tight fit try it some time.
Perhaps a better question would be which art would best prepare you to fight multiple opponents...