Leonardo da Vinci was fascinated with the form of the spiral. His helicopter takes the form of an aerial screw, following the example of a device earlier brought to Europe from Asia in the form of a children's toy. He wrote of his design for the helicopter: "If this instrument made with a screw be well made — that is to say, made with linen of which the pores are stopped up with starch — and be turned swiftly, the said screw will make its spiral in the air and it will rise up high."