According to Leonard Goldwater, author of Mercury: A History of Quicksilver, the ancient Turks used camels' urine to accelerate the process of softening camel hair to make felt. The Crusaders brought this technology to Western Europe, where French hatters refined it further on the pelts of rabbits, rats, and other small animals.

Lacking urine from camels, French craftsmen sought other sources. They soon realized the best suppliers of urine were the felt makers themselves.