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. An even earlier text, the "Wujing Zongyao" (武经总要, "Collection of the Most Important Military Techniques"), written in 1044 by Song scholars Zeng Gongliang and Yang Weide, described the use of three spring or triple bow arcuballista that fired arrow bolts holding gunpowder. Although written in 1630 (second edition in 1664), the "Wulixiaoshi" of Fang Yizhi said that fire arrows were presented to Emperor Taizu of Song in 960. Even after the rocket was invented in China the fire arrow was never entirely phased out: it saw use in the Second Opium War when Chinese used fire arrows against the French in 1860.