Reading the Spycraft material end to end, the same move keeps happening with different objects. Knowing men: read the outward form (the face, the bearing, who he stays close to when poor) to infer the inward nature. Knowing terrain: read the outward configuration (marsh-and-mound, valley-front, water-flow) to infer whether the ground will hold you or kill you. Knowing the sky: read the cloud-ch'i above an army or a city to infer morale, intent, the general's courage, the coming victory. Three chapters, one method — the visible exterior is an index of the hidden interior.
And the failure mode is identical in all three. The form can be staged (the false-defector's grievance, the dummy-chariot dust, the faked spirit-omen). And even when the form is honest, it reports the permanent and goes blind to the recent change — the female-typed city that has quietly hardened, the man who has steeled himself against his "type," the timid general who has resolved to die today. Physiognomy of a person, physiognomy of a hill, physiognomy of a cloud: same promise, same blind spot.
The Live Wire.
Links: Sun Pin's Male & Female Cities, Physiognomy & Character Reading, The Cloud-Ch'i Reading Doctrine.