In Proverbs 30:19, the way of which creature on a rock is too wonderful to understand?

Answer: A snake

Agur names the way of an eagle in the sky, a snake on a rock, a ship at sea, and a man with a maiden.

“There are three things too wonderful for me, four that I cannot understand: the way of an eagle in the sky, the way of a snake on a rock, the way of a ship at sea, and the way of a man with a maiden.”— Proverbs 30:18-19 (BSB)