Yeah, getting clear information is hard. This bulletin on horses and horsepower from 1926 is pretty great, though it also doesn't answer the question very clea

Yeah, getting clear information is hard. This bulletin on horses and horsepower from 1926 is pretty great, though it also doesn't answer the question very clearly: https://lib.dr.iastate.edu/cgi/viewcontent.cgi?article=1466&context=bulletin https://lib.dr.iastate.edu/cgi/viewcontent.cgi?article=1466&... There's a bunch of load pull tests there, but they are only done on teams, never on a single horse.