Seal it with a swat

When did we start signing our names to contracts? While the practice of signing one's name to a document does go way back, Slate recently revealed that it was also common to use wax seals to indicate authenticity between the 6th and 17th centuries.

Another more casual way to seal an agreement was cutting off a lock of one's hair and giving it to the other party. During the 13th century, agreements were sometimes marked with a slap, or some other traumatic act. The theory was that both parties would remember not only the injury but the accord that was reached on its infliction.

So spankings were legally valid and recognized as memory improvement aids.