In February 1967, it was revealed that two notebooks by the great 15th-century Italian artist, Leonardo da Vinci, that had been lost for centuries, had been discovered in the national library in Spain. Louise Hidalgo talks to two people with a personal interest in the discovery, Da Vinci scholar Pietro Marani, and robotic engineer, Mark Rosheim, who used Leonardo's drawings to recreate the artist and inventor's lost Robot Knight. (Photo: A self-portrait by Leonardo da Vinci dated circa 1500. Credit: Hulton Archive/Getty Images)