I was musing a bit about bicycles a while back, and how far back in time they could conceivably have been feasible and practically useful (i.e. earlier than 1820). I was imagining the difficulty of making it lightweight with pedals, rubber tires, a comfy seat, etc. Would need good roads too. Well, maybe doesn't really need all that: https://en.wikipedia.org/wiki/Chukudu A regular bicycle might be less practical in some ways. Maintenance. Cargo capacity.