In 1972, Spruytte published "Ancient Harness Systems" which argued that there were at least three ancient traction systems shown in art, none of which choked the horses. The shoulder traction (ancient Egyptian) and breast traction (Greek and Roman) artwork had been mis-seen and mis-drawn as a composite that matched neither. This he sought to demonstrate by building reproduction chariots and harness, and running them with suitable teams. These had to be borrowed ponies as horses were too large for the surviving Egyptian chariot he used as a model.