Hydromancy

Hydromancy is the supposed art of divining by water. The Persians, according to Varro, invented it; Pythagoras and Numa Pompilius made use of it; and we still admire the like wonderful prognosticators.

Hydromancy was extensively practised by the Egyptian priests and sorcerers[.]

Hydromancy, like many other methods of divination, seems to have originated in Babylonia and reached the Greco-Roman world via Egypt, in the first century b.c. or earlier.