The sleep state that the rigidbody will initially be in.
Sleeping is an optimisation that is used to temporarily remove an object from physics simulation when it is at rest. This property chooses whether the rigidbody should start off asleep, awake or have sleeping turned off altogether.
See the Physics Overview in the manual for more information about Rigidbody sleeping.
See Also: Sleep, IsSleeping, WakeUp, Rigidbody.Sleep.