on mythbusters they tried to use standard balloons though, like the type at a kid's birthday party or something. These ones are clearly a ton bigger.
the first guy to do it had weather balloons, and was actually spotted by a plane that was approaching Los Angeles, and saw some dude in a chair float by.
How fuckin crazy would that be, to be the pilot that spotted someone in a lawn chair floating by when you're at like, 15,000 feet?