Detail of cavalrymen.
No evidence is available for this source.
The complexity of these Trajanic scenes employed on the Arch of Constantine would seem to suggest that the carvers were working from sketches or even maquettes. It must have been an enormous challenge to fit all of these figures into the scene without cutting anyone off. If maquettes were used then they were probably for working out the structure of the composition rather than for the production of accurate copies considering the pointing machine is a much later invention.