The first studies on helicopters were well in advance of the first airplanes. Leonardo da Vinci is credited with having first thought of a machine for vertical flight, the "airscrew," the design for which, dated 1493, was only discovered in the 19th century. It consisted of a platform surmounted by a helical screw driven by a somewhat rudimentary system, not unlike that of rubber-powered model aircraft. The great Tuscan genius wrote that if this instrument in the form of a screw were well made of linen, the pores of which had been stopped with starch, it should, upon being turned sharply, rise into the air in a spiral. However his design was never put to any practical use.