According to an anecdote, Thomas Edison had a summer residence he was very proud of. He enjoyed showing visitors around the property and pointing out various inventions. At one point, people had to pass through a heavy turnstile to get back to the house.

One visitor asked Edison why, with all the other clever gadgets around, he had such a heavy turnstile. Edison replied, “Well, you see, everyone who pushes the turnstile around pumps eight gallons of water into the tank on my roof.”