The Square Surcharge: USPS Favors Rectangles
BUFFALO, N.Y. -- The square has four equal sides and four right angles. It is a regular shape. To the U.S. Postal Service, however, the square is "unusual." Its sorting machines, built for oblongs, can't find the address on a square envelope. People have to do it. That's why the post office imposes the square surcharge. (Alternative link to the article here.)
How would UPS handle it?