Leonardo da Vinci sketched a ball bearing using balls between rings to reduce friction between moving parts.
Around 1498, Leonardo drew a bearing arrangement in which small balls could roll between surfaces instead of allowing one surface to slide directly against another. Rolling contact generally produces less friction than sliding contact, making rotation smoother and reducing wear. His studies were connected with mechanical projects and the movement of shafts.
Leonardo did not invent every form of bearing, and his sketch was not a modern sealed bearing. The balls in the design could still rub against one another, which would reduce efficiency. Practical bearing cages and standardized manufacturing developed much later.
The drawing is historically significant because it clearly anticipates a central principle of modern bearings. It also illustrates Leonardo’s habit of isolating friction as an engineering problem and solving it through geometry and controlled motion.