 Jiao Yu called the earliest fire arrows shot from bows (not rocket launchers) "fiery pomegranate shot from a bow" because the lump of gunpowder–filled paper wrapped around the arrow below the metal arrowhead resembled the shape of a pomegranate.He advised that a piece of hemp cloth should be used to strengthen the wad of paper and sealed with molten pine resin.Although he described the fire arrow in great detail, it was mentioned by the much earlier Xia Shaozeng, when 20,000 fire arrows were handed over to the Jurchen conquerors of Kaifeng City in 1126.