sleeping_wolf is right on. I once sent my aunt a small paper airplane in the mail. I taped it together (across the little ravine in the top of the plane), wrote a bit of a message and drew a couple sketches on the various sides, put the address on the left wing, and stuck about 60 cents of postage on the right wing. I dropped it in a mailbox on a streetcorner in San Francisco, and just a few days later it arrived, fully intact and undamaged, in my aunt's mailbox in Boise. The USPS is an impressive thing.