Huolongjing

While the Chinese are widely known as the inventors of gunpowder, there are some surprisingly early innovations that are more obscure. These are catalogued in the early Ming dynasty book Huolongjing (Fire Dragon Manual in English) written in the 14th century.

The book showcases various gunpowder-powered devices ranging from flamethrowers to grenades to mines, both land and naval. It even has an explanation of the evolution of the 10th century exploding fire-arrow into a winged rocket. It also includes descriptions of various proto-firearms such as the fire lance, which fires flaming shrapnel like some sort of firey shotgun. There's also cannons complete with exploding cannonballs.

Although the western world surpassed the Chinese in terms of gunpowder technology in the 15th century, Huolongjing shows us what had been done with it for centuries before westerners ever laid eyes upon the destructive powder.