A toilet was a device upon which an individual could deliver personal waste to either a septic tank or a sewer system. Toilets were at first a luxury item for many people in the early 20th century, however had become more commonplace by the 1950s. They were usually made in porcelain.
On November 5, 1955, Emmett Brown was hanging a clock while standing on his toilet. The porcelain on the toilet was wet and he slipped, hitting his head on the sink. When he came to, he had a vision of his flux capacitor. That toilet is later seen in Doc's mansion when Marty returns to 1955 for the second time.