It was an invention of Heron of Alexandria, which permitted the automatic opening of the temple gates after sacrifice on its altar creating in the faithful the impression of a miracle.
In the underground of the temple, the chains of a balance were wrapped around the rotation axles of the temple doors. The balance had a container at one side and a counterweight at the other. With the fire of sacrifice, the air inside the closed container of the altar expanded and went through a pipe to a closed container with water. The water was pushed through a siphon and was led to the container on the balance that tipped outweighing the counterweight, thus, causing the diversion of the balance towards this. The chains of the balance rotated the axles and the temple gates opened. After the sacrifice, the phenomena were reversed and the temple doors closed.