Wujing Zongyao
Gunpowder had already been invented prior to the "Wujing Zongyao" by Chinese alchemists in the 9th century. Early references to gunpowder can be found in the Daoist book "Zhenyuan miaodao yaolue", written circa 850, and gunpowder was utilized in Chinese warfare as early as the 10th century in fire arrows and gunpowder fuses used to light the Chinese two-piston flamethrower.