one of my friends sent me this manual on tantra. its supposed to be derived frm an ancient samurai art that exercises every muscle in the body, in this case the penis(muscle). it is supposed to keep u going for at least half an hour and quickly regain erections after cuming. the manual seem very detail and the exercises seems time consuming. i dunno if i should try it or not coz u must make it like a commitment. anyone who has and is willing to share thier experiences please comment.