The origin of whirligigs is unknown. Both farmers and sailors use weather vanes and the assumption is one or both groups are probably the originators. By 400 BC the bamboo-copter or dragon butterfly, a helicopter-like rotor launched by rolling a stick, had been invented in China. Wind-driven whirligigs were technically possible by 700 AD when the Sasanian Empire began using windmills to lift water for irrigation. The weather vane, which dates to the Sumerians in 1600–1800 BC, is the second component of wind-driven whirligigs. In early Chinese, Egyptian, Persian, Greek and Roman civilizations there are ample examples of weathervanes but as yet, no examples of a propeller-driven whirligig. A grinding corn doll of ancient Egyptian origin demonstrates that string-operated whirligigs were already in use by 100 BC. The first known visual representation of a European whirligig is contained in a medieval tapestry that depicts children playing with a whirligig consisting of a hobby horse on one end of a stick and a four-blade propeller at the other end. For reasons that are unclear, whirligigs in the shape of the cross became a fashionable allegory in paintings of the fifteenth and sixteenth century. An oil by Hieronymus Bosch, probably completed between 1480 and 1500 and known as the Christ Child with a Walking Frame, contains a clear illustration of a string-powered whirligig. A book published in Stuttgart in 1500 shows the Christ child in the margin with a string-powered whirligig. The Jan Provoost attributed late sixteenth-century painting Virgin and Child in a Landscape clearly shows the Christ child holding a whirligig as well. The American version of the wind-driven whirligig probably did not originate with the immigrant population of the United Kingdom as whirligigs are mentioned in early American colonial times. How the wind-driven whirligig evolved in America is not fully known, though there are some markers. George Washington brought whilagigs home from the Revolutionary War. What type is unknown. By the mid-18th century weathervanes had evolved to include free moving "wings". These "wings" could be human arms; pitchforks; spoons, or virtually any type of implement. The 1819 publication by Washington Irving of The Legend of Sleepy Hollow contains the following description: "a little wooden warrior who, armed with a sword in each hand, was most valiantly fighting the wind on the pinnacle of the barn". By the latter half of the 19th century, constructing wind-driven whirligigs had become a pastime