An article of furniture is disclosed. The article of furniture comprises a stool configured to be used on a generally horizontal surface such as a floor. The stool comprises a seat and a base comprising a rounded bottom surface configured to rest upon the floor. A mass is positioned beneath the seat so that the base is at equilibrium in a first tilted orientation relative to the floor. The base can be tilted to second tilted orientation relative to the floor by tilting the rounded bottom surface of the base relative to the floor.