catoptromancy

Catoptromancy (Gk. katoptron, mirror, and manteia, divination), also known as captromancy or enoptromancy, is divination using a mirror.Pausanias, an ancient Greek traveler, described as follows: Before the Temple of Ceres at Patras, there was a fountain, separated from the temple by a wall, and there was an oracle, very truthful, not for all events, but for the sick only. The sick person let down a mirror, suspended by a thread till its based touched the surface of the water, having first prayed to the goddess and offered incense. Then looking in the mirror, he saw the presage of death or recovery, according as the face appeared fresh and healthy, or of a ghastly aspect.
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(n.)
A species of divination, which was performed by letting down a mirror into water, for a sick person to look at his face in it. If his countenance appeared distorted and ghastly, it was an ill omen; if fresh and healthy, it was favorable.
  

Divination based on how a face appears when viewed in a mirror underwater