Another armchair pilot story - you know attaching helium balloons to your chair to go out flying - has emerged. Man Flies 193 Miles in Lawn Chair | LiveScience I thought the old story was an urban myth. This one is on a reputable science site.
I calculate that if man and chair weigh about 80kg, then he needs about 60 m3 of helium to get lift, and that is before considering the weight of the balloons. He also took, according to the story, 20 gallons of water as ballast, that's another 70kg or so, and a parachute. So the total load is now 150kg, say, probably a bit more. Does "105 large helium balloons" really add up to all that. Add on another kg for each balloon, which would be quite light for a balloon strong enough to hold over 1 m3 of helium. Now we have 250kg, about 200m3 of helium, each ballon is a little over 2 m3. That would mean that the cloud of balloons above him occupies a cube roughly 6 m each side, that is the size of about 3 double-decker buses.