A new Wired article tells the interesting story of Leonardo da Vinci's 500 year-old design for a three-wheeled, programmable robot. Originally described as a "car" when the drawings were discovered, further research revealed the device was more likely a robot. The robot was powered by springs and guided by geared disks and cams. An earlier BBC article also describes the model recently built from the original plans. Drawings, exploded diagrams, and photos of a model can be found on the Discovery Channel website. Their are also drawings of another, humanoid robot Leonardo design but never built. The researcher mentioned in the wired story, Mark Rosheim, is working on a book to be called Leonardo's Lost Robots. His home page also has a more detailed article about the reconstructed robot.