ANCIENT VENDING MACHINE

One of the most unusual inventions of Alexandria was definitely vending machine, invented by Heron (Hero Ctesibius 10 – 70 AD). He invented many gadgets and wrote pages and pages about them.
Heron’s vending machine was constructed for Egyptian temples. This vending machine would accept a five Drachma coin in exchange for a small supply of holy water to wash hands and face. When a coin was inserted it lifted a plug in the water urn and allowed a small amount of liquid to escape. When the coin had rolled into the collection bin inside the machine, the balance returned to normal stopping the flow of water. The priests would collect coins at the end of each day.

Vending machine function

English translation of Heron's book Pneumatics:

"If into certain sacrificial vessels a coin of five drachms be thrown, water shall flow out and surround them. Let A B C D (fig. 21) be a sacrificial vessel or treasure chest, having an opening in its mouth, A; and in the chest let there be a vessel, F G H K, containing water, and a small box, L, from which a pipe, L M, conducts out of the chest. Near the vessel place a vertical rod, N X, about which a lever, O P, widening at O into the plate R parallel into the bottom of the vessel, while at the extremity P is suspended a lid, s, which fits into the box L, so that no water can flow through the tube L M: this lid, however, must be heavier than the plate R, but lighter than the plate and coin combined. When the coin is thrown through the mouth A, it will fall upon the plate R and, preponderating, it will turn the beam O P, and raise the lid of the box so that water will flow; but if the coin falls off, the lid will descend and close the box so that the discharge ceases. (37)" 1

There is a thought that Heron’s machine was built under influence of the Philo of Byzantium’s (280 BC – 220 BC) hand washing machine.
“A counterweighted spoon, supplied by a water tank, tips over in a basin when full releasing a pumice in the process. Once the spoon has emptied, it is pulled up again by the counterweight, closing the door on the pumice by the tightening string. Remarkably, Philon's comment that "its construction is similar to that of clocks" indicates that such escapements mechanism was already integrated in ancient water clocks.” 2 



Picture Source: http://www.underthepier.com/19_vending_machines.htm
Source 1: Source: www.neatorama.com
Source 2:Source: http://en.wikipedia.org/wiki/Philo_of_Byzantium