הלכה אויף אסתר 8:8

A ring whereon the image of a man is engraved as a seal, if the image be protruding, he is forbidden to keep it in his hand, but is permitted to have the idolator make an impression on wax therewith; if the image be inwardly engraved he is permitted to keep it in his hand, but forbidden to have the idolator make an impression on wax therewith, because the inwardly engraved image will appear protruding from the wax seal. It is likewise forbidden to sketch the image of the sun, of the moon, of the stars, of the planets, and of angels; for, it is said: "Ye shall not make with me", that is to say: ye shall not make images like unto My ministers, who minister before Me Above, not even upon a tablet. Images of cattle and other living creatures, save man, and images of trees and plants and the like, one may sketch, even though the image be protruding.¹⁷Ibid.; Mekilta, Ex. 20. C.G.