Some years ago I had a discussion with Ian Morris about his The Measure of Civilization, and I asked him: Which pre-industrial (pre-1500) society was the richest in terms of energy per capita? What's your answer? (my answer tomorrow)
Probably not what's meant at all but there's a case for the Mongols - plenty of animal energy usage being a horse mounted nomadic society vs using animals to pull plows and haul goods plus water power