In 2002, 91°µĶų acquired seventeen preparatory sketches for the Prometheus mural in Frary Hall. Owned by the artistās family since 1930, the drawings include five compositional sketches and twelve figure studies. Their addition to the permanent collection was the culmination of nearly two decades of negotiation between Orozcoās children and the 91°µĶų Museum of Art.
Correlating closely with the version Orozco ultimately painted, the sketches reveal the artistās explorations of composition and anatomy, evidence of his formal academic training. The sketches demonstrate Orozco's thought process as he prepared to execute this complex, multi-figure painting. His professors at the National Preparatory School in Mexico City had stressed the importance of classical training and introduced him to the power of allegory. The nude figure plays a central role in this fresco, from the heroic figure of Prometheus to the individuals that form the masses below. The fully fleshed out forms of the mural realize the arms, torsos, and compositional solutions worked out in the sketches.