One of the great rabbinic scholars from the Geonic period, Rabbi Hai Gaon (939-1038 CE) wrote a responsum wherein he mentions as something "well-known" that that idolatrous temples would set up apparatuses that use science/technology in order to convince the uneducated of the efficacy of their cultic practices. He notes, for example, that they would commonly have medicinal remedies at these temples so that the sick might be healed by visiting. He compares this to the Talmudic legend of Gehazi using magnetics to give the illusion that Jeroboam's Golden Calves were suspended in the air. Is there any documentation of these or other examples of such use of scientific knowledge or technology in pagan temples?
The way I understand it, in contemporary terms, they might have hung something like an magic eye image on the wall of the temple and tell people that if they look closely, the deity will send them a secret message that is not plainly visible in the picture, and then when people finally see the hidden image, they would take that as proof of the efficacy or supernatural powers of the deity. Do we have any evidence of this sort of stuff going on in pagan temples?