The Straight Dope: Can you walk on hot coals in bare feet and not get burned?:

"But fire-walking in some parking lot is for wimps. If you're hard core there are more challenging methods. I've just spoken to my bud Jearl Walker, the former Scientific American columnist and, it turns out, the G. Gordon Liddy of physics.

"As a classroom demo of the Leidenfrost effect, Jearl not only walked on hot coals (he gave it up after getting badly burned once--he was so cool his feet didn't get sufficiently damp), he also dips his bare hand in water and then plunges it momentarily into a vat of molten lead, 700 degrees Celsius. Says Jearl, who's even done this on Johnny Carson, 'there is no classroom demonstration so riveting as one in which the teacher may die.' It'd definitely penetrate my ennui, I'll tell you. Just don't volunteer in Jearl's class when he asks someone to give him a hand."