In the diagram shown, the "working body" (system), a term introduced by Clausius in 1850, can be any fluid or vapor body through which heat "Q" can be introduced or transmitted through to produce work. In 1824, Sadi Carnot, in his famous paper "Reflections on the Motive Power of Fire", had postulated that the fluid body could be any substance capable of expansion, such as vapor of water, vapor of alcohol, vapor of mercury, a permanent gas, or air, etc. Though, in these early years, engines came in a number of configurations, typically "QH" was supplied by a boiler, wherein water boiled over a furnace; "QC" was typically a stream of cold flowing water in the form of a condenser located on a separate part of the engine. The output work "W" was the movement of the piston as it turned a crank-arm, which typically turned a pulley to lift water out of flooded salt mines. Carnot defined work as "weight lifted through a height".