Wujing Zongyao
The "Wujing Zongyao" records detailed descriptions of gunpowder weapons such as incendiary projectiles, smoke bombs, fire arrows, and grenades. It documents incendiary projectiles containing low-nitrate gunpowder, which were launched from catapults or lowered down from city walls onto besiegers. Examples of these incendiaries include the "swallow-tail" incendiary (; "yanweiju") and the flying incendiary (; "feiju"). The swallow-tail incendiary was made of straw tied together and dipped in fat or oil. Chinese soldiers defending a city under siege would light the incendiary and lower it onto any wooden structure of the invading army to engulf it in fire. The flying incendiary visually resembled the swallow-tail incendiary, but was lowered using an iron chain from a swape lever installed within the walls of the city. The book also describes an 'igniter ball' used in warfare and for finding the firing range. The "Wujing Zongyao" stated the following: