Leonardo da Vinci sketched a ball bearing centuries before modern bearings.
Around the late fifteenth century, Leonardo drew a bearing arrangement in which balls separated moving surfaces. The basic purpose was to reduce friction by replacing sliding contact with rolling contact.
His design included a cage-like arrangement intended to keep the balls from crowding together. That feature is especially important because loose balls can bunch up and fail to distribute motion efficiently. Leonardo’s sketch shows that he understood both the friction problem and the need to manage the rolling elements.
Leonardo did not invent every form of bearing, and his drawing was not the same as a modern sealed ball bearing. Later engineers developed more durable materials, precise manufacturing, lubrication systems, and standardized races. His design is nevertheless an early documented example of a ball-bearing concept.