Leonardo da Vinci, the great Italian painter, was also an innovator in the field of mechanics. He created many sketches which were the predecessors to several important 19th and 20th century inventions. Da Vinci created a sketch of a primitive tank. His tanks looked more like flying saucers on wheels. A boxier war tank was later created and used during World War I. He also sketched an early version of a helicopter, which "is said to have inspired Igor Sigorsky" as he invented the modern helicopter. It also could have been the model for which the screw propellor, which is found on modern boat motors, was based on. He also sketched models of ball bearings, which are found in everything from airplanes to computers. They are also essential to manufacturing. He created sketches of scuba diving gear.