The tank shown in the picture was designed by Leonardo. It is a heavy vehicle shaped like a tortoise with cannons all round it and perhaps reinforced with metal plates. Some people had thought of moving it with sails, but Leonardo's solution was a system of gears moved by cranks worked by eight men inside. He even thought of using horses instead of men but the risk of the animals panicking in such a tight, noisy space made him change his mind.   Close