All 4 Uses

poise
in
As I Lay Dying
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The sun, an hour above the horizon, is poised like a bloody egg upon a crest of thunderheads; the light has turned copper: in the eye portentous, in the nose sulphurous, smelling of lightning.†
Chpt 10
He sits lightly, poised, upright, wooden-faced in the saddle, the broken hat raked at a swaggering angle.
Chpt 27 *

poised = in control and prepared to move as needed
He sits erect, poised, looking quietly and steadily and quickly this way and that, his face calm, a little pale, alert.†
Chpt 34
Then the downstream one vanishes, dragging the other with him; the wagon sheers crosswise, poised on the crest of the ford as the log strikes it, tilting it up and on.†
Chpt 34

Definitions:

(1) (poise)
calm, confident, and in control—especially in movement, behavior, or when ready to act
(2) (meaning too rare to warrant focus)
Much more rarely, poise is a technical word referencing a unit of dynamic viscosity.