When the Mongols ruled China they were very scared of a revolt from the native Chinese so they took many measures including forbidding Chinese to carry any weapons to prevent that from happening. However, they did not stop the Chinese custom of exchanging crescent moon shaped cookies during a full moon. These cookies carried messages which allowed them to organize an eventual revolt.

(Book – The Discoverers : A History of Man’s Search to Know His World and Himself – Daniel J. Boorstin)