Leonardo da Vinci sketched a ball bearing using balls placed between two rings to reduce friction.
The arrangement allowed one ring to rotate relative to the other while the balls rolled between them. Rolling contact generally creates less resistance than sliding contact, which is the basic principle behind ball bearings.
Leonardo’s sketches date from the late 15th or early 16th century and show his understanding of how friction affects machines. Some designs included separators intended to keep the balls apart, an issue that remains important in bearing engineering.
Leonardo did not create the complete modern bearing industry. His drawings were conceptual studies, and practical ball bearings developed much later with improved materials, manufacturing, and lubrication. The sketch is nevertheless an early documented bearing concept.