Adam Clarke on Leviticus 19:26

Neither shall ye use enchantment - לא תנחשו lo thenachashu. Conjecture itself can do little towards a proper explanation of the terms used in this verse. נחש nachash; See note at Gen 3:1 (note), we translate serpent, and with very little propriety; but though the word may not signify a serpent in that place, it has that signification in others. Possibly, therefore, the superstition here prohibited may be what the Greeks called Ophiomanteia, or divination by serpents.

Nor observe times - ולא תעוננו velo teonenu, ye shall not divine by clouds, which was also a superstition much in practice among the heathens, as well as divination by the flight of birds. What these prohibitions may particularly refer to, we know not. See Clarke's note on Gen 41:8.