Yoga Sūtra Chapter Three verse 21
kāya-rūpa-saṃyamāt-tat-grāhya-śakti-stambhe cakṣuḥ prakāśa-asaṃprayoge-antar-dhānam ||21||
From complete restraint on form of body dissappearance;
that suspension of the power of what is to be grasped
is disengagement of the eye and light.