These rather gorgeous images are from an eighteenth-century book consisting of 36 ink drawings showing precise iconometric guidelines for depicting the Buddha and other figures. I stumbled across it today on a site called The Public Domain Review, which draws attention to non-copyright media of all sorts that are available for general use.
As the site points out, “The concept of the ‘ideal image’ of the Buddha emerged during the Golden Age of Gupta rule, from the 4th to 6th century. As well as the proportions, other aspects of the depiction – such as number of teeth, color of eyes, direction of hairs – became very important.”
It’s worth checking out the other images in the collection.