Work and experience create and broaden our knowledge. It is of value to test the veracity of the indirect book knowledge by applying it to reality. Sir Isaac Newton, applied mathematics to his personal experience, resulting the discovery of kinetic theory. Nicholus Copernicus, through extensive observation and existing scientific analysis, calculated the earth and other planets’ orbit around the sun. Such knowledge is now easily assessable in textbooks, but would require decades of work on our own to research and understand that phenomenon.
Christopher Columbus As a child, he helped his father as a weaver. He always liked the sea. Genoa was an important seaport. There is no doubt that as a child he caught rides on ships. He had little schooling but was a genius with the sea. His plan was not to prove that the world was flat, but it was to find a shortcut to the Spice Islands. He wanted to establish a city there for trade, seaports, and much more. When he grew into a man he was interested in sailing to Asia by going west.
Leonardo da Vinci is best remembered as the painter of the Mona Lisa (1503-1506) and The Last Supper (1495). But he's almost equally famous for his astonishing multiplicity of talents: he dabbled in architecture, sculpture, engineering, geology, hydraulics and the military arts, all with success, and in his spare time doodled parachutes and flying machines that resembled inventions of the 19th and 20th centuries.
He made detailed drawings of human anatomy which are still highly regarded today. Leonardo also was quirky enough to write notebook entries in mirror (backwards) script, a trick which kept many of his observations from being widely known until decades after his death.