What type of machine did Leonardo da Vinci sketch for grinding mirrors?

Leonardo da Vinci sketched a mirror-grinding machine for shaping and polishing reflective surfaces.

The design used mechanical motion to help grind a curved mirror more evenly than hand work alone. Leonardo was interested in optics, reflection, and the geometry of curved surfaces, so mirror making fit naturally within his broader investigations.

Renaissance optical instruments depended on carefully finished glass or metal surfaces. A machine that maintained regular motion could improve consistency, although Leonardo’s surviving drawings do not show that he established a modern industrial production system.

The device is sometimes described loosely as a telescope invention, but that overstates the evidence. Leonardo studied optics and proposed many related devices; the secure point is that he designed machinery for grinding mirrors.