In reference to Buddhist art what was the symbol used to represent the sermon delivered by Buddha at Sarnath?

The Wheel

To comprehend Buddhist sculpture, art historians needed to acquaint themselves with the hagiographies of the Buddha. According to these accounts, the Buddha achieved enlightenment while meditating under a tree. In the early days of Buddhist art, sculptors chose not to depict the Buddha in human form but rather conveyed his presence through symbolic representations. For instance, the empty seat symbolized the Buddha's meditation, while the wheel served as a frequent symbol representing his first sermon, delivered at Sarnath.