This activity is great practice for learning to see values (lights and darks) and duplicate them in your drawings. Younger students may only have the patience to do two or three of these, while older students may want to do several more.
Three horses galloping across a bare landscape, painted in gouache on paper. Perhaps from a manuscript illustrating the capture of Rakhsh by Rustam, as described in the Shahnameh century, Persia (modern Iran).
These cave paintings amaze me: Horse heads, Chauvet Cave. Fourteen different animal species are depicted in the Chauvet Cave. Here, three beautiful horses' heads face one another. Someday I want to see cave paintings in person.