瑜伽論記 4.292

4.292

言由觀察空，或時思惟，內外空性者，明初行者將彼無學內外空義類，觀自身內外空性總觀察之，由此觀力心俱證會內外空性。

The statement "by means of the emptiness of observation, at times reflecting on internal and external emptiness" clarifies that the initial practitioner takes those models of internal and external emptiness of the one beyond training, and generally observes them, contemplating the internal and external emptiness of their own body; by the power of this contemplation, the mind simultaneously realizes and accords with internal and external emptiness.