Watt's engine counter, c.1781.Power and money! Watt was keen to get his due reward for creating the engine, and designed this engine counter so his customers could be charged for the exact amount of work done. The counter sat on the engine’s beam in a sealed box, for which only Boulton & Watt's agents had a key. As the beam rocked up and down, a pendulum inside counted the working strokes, and the owner was billed accordingly. Paying for power in this way continues today with the electricity or gas meters in people's homes.
Science Museum, London