Leonardo da Vinci sketched a ball bearing to reduce friction between moving surfaces.
His drawings show balls placed between rings or supports so that rolling contact could replace much of the sliding contact found in ordinary joints. Rolling generally produces less resistance than sliding, making the arrangement useful for rotating machinery.
Leonardo’s sketches are among the early historical examples associated with ball-bearing ideas, but he did not create the modern standardized bearing industry. The drawings also do not prove that he built a practical, durable bearing for a machine.
A ball bearing is different from a roller bearing: the first uses spherical rolling elements, while the second uses cylindrical or other elongated rollers. Modern bearings also depend on carefully manufactured races, cages, lubrication, and precise tolerances that were not available in Leonardo’s workshop.