I have never seen that trick, and trust me I have seen quite a few, they aren't as popular nowadays. If I saw what he was doing I would probably figure it out. Of course he did indeed follow the primary rule, make it look impossible, until their is money on the bar. When people are really drunk I start to brag about how i can stay under water for 10 minutes without any scuba gear or breathing devices, they start saying it is impossible, and i say not at all I can do it all the time. As they argue more I say okay, my entire body will be under water and I will not use anything to help me breath while I am under water. When the drunker people start taking money out of their pockets, I match it and ask the bartender for a glass of water and hold it over my head.
The best one I do that involves physics is the fork and spoon on one end of a toothpick while the other end of the toothpick dangles over the rim of a glass, once i get it balanced, I light the part of the toothpick on the inside section of the rim, until it is only on the rim. Balance does not happen, because of an equal amount of weight, but the distribution of torque in a system.