Every pre-modern wagon had a big old bucket of grease hung at the side of it. It was needed to keep the axle continuously lubricated. (Sayings about wheels and

Every pre-modern wagon had a big old bucket of grease hung at the side of it. It was needed to keep the axle continuously lubricated. (Sayings about wheels and grease are preserved to this day.) Theoretically, a two-wheeled transportation contraption could have been made, but having to carry the grease with you would make it pointless.