"What if you had two swallows, with a string attached to it?.....gripping by the husk"
african or european swallows
One source says 1 liter of helium can lift 1 gram.
Translating to the other measurement system, you get
1 gram = .0022 pounds
200 pounds = about 91,000 grams
1 liter = .035314 cubic feet
91,000 times .035314 cubic feet = about 3214 cubic feet.
Thus, not counting the weight of the balloon (or whatever is holding the helium), it would take more than 3,000 cubic feet of helium to lift a 200-pound person off the ground.
get out your calculators