A vending machine is a machine in which customers put money in and then pay for themselves. Vending machines originated from Greece.
In the Christian era, the Greek scientist Hero distributed holy water to the church and built a holy kettle. Anyone who inserts a 5 drachma coin will have a certain amount of holy water spit out from the spout. The faithful men and women at that time were all dumbfounded by how efficacious this divine pot was, thinking that the gods were appearing and collecting money from its children. Hero invented this magical pot, which was actually a vending machine. There is a lever in the divine pot. One end of the lever is connected to the plug of the water outlet, and the other end is aligned with the coin insertion hole. The coin falls from the hole and hits one end of the lever. The lever loses its balance, one end goes down and the other end tilts up. Then the plug of the water outlet is pulled out, and the holy water flows out. When the coin falls into the pot along the descending end, the weight on the lever end is gone, the lever returns to balance, the upturned end also falls, and the plug blocks the water outlet again.
The principles of various vending machines today are influenced by the holy kettle.