Postal Experiments from The Journal of Improbable Research

We sent a variety of unpackaged items to U.S. destinations, appropriately stamped for weight and size, as well as a few items packaged as noted. We sent items that loosely fit into the following general categories: valuable, sentimental, unwieldy, pointless, potentially suspicious, and disgusting.

Helium balloon.
The balloon was attached to a weight. The address was written on the balloon with magic marker; no postage was affixed. Our operative argued strongly that he should be charged a negative postage and refunded the postal fees, because the transport airplane would actually be lighter as a result of our postal item. This line of reasoning merely received a laugh from the clerk. The balloon was refused; reasons given: transportation of helium, not wrapped.