Before steam power became widespread, some locomotives were powered by horses on treadmills. This version, dubbed Impulsoria by Italian inventor Clemente Masserano, was driven by four horses that walked continuously at their best speed; a gearbox could be set to forward, reverse, or neutral.

The “horse locomotive” successfully climbed a hill at trials in London in 1850 and was displayed at the Great Exhibition the following year. It was hoped that a final version might reach 20 mph, outrunning the steam engines of the day, but mechanical engines soon surpassed it.