Musar על סוכה 55:4

In the world, there are cold winds and warm winds. So is it with man. When he opens his mouth and blows, then his breath is warm. And when he closes his mouth and blows, then his breath is cool. The thunders of the world are like the voice in man; the lightning of the world is in the face of man when it shines like lightning. There are constellations in the world, and those who view the stars can tell the future from them. So are there signs in man. When a man has a rash, which does not come from a boil or a louse or a mite, experts in this matter can foretell the future. And so it is with the lines in the palm of a man's hand and with the form of his features that people may know the future. Now this wisdom was in the possession of the wise men of old but has been forgotten by the later ones. Similarly the wise men can tell the future by trees and herbs, and this is according to what they said concerning Rabban Johanan ben Zakkai that he knew the language of the date palms (Sukkah 28a). The meaning of this is that he was expert enough to perceive the motion of the date palms and from this he could tell the future (Aruch 68).