Maybe the weight is in small print. lol. Seriously though, the weight limit on a flat rate envelope or box is 70 lbs. Unless you're mailing something like a cannonball I can't imagine anything that heavy fitting in those boxes AND can't imagine the boxes not falling apart.
Actually even a cannonball might not fit.
Wash: "A man walks down the street in that hat, people know he's not afraid of anything."
Jayne: "Da*n straight."
-- my recipes