Yoga Sūtra Chapter Three verse 21
कायरूपसंयमात् तत्ग्राह्यशक्तिस्तम्भे चक्षुः प्रकाशासंप्रयोगेऽन्तर्धानम् ॥२१॥
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.
Commentaries and Reflections
Commentary by T Krishnamacharya:
Commentary by TKV Desikachar:
Commentary by S Ramaswami:
“By Saṃyama on one’s own bodily form the power of revealing itself is stopped.
By making the observer unable to use the instrument of perception, or his mind, the Yogi is not observed.
So far types of contemplation or Saṃyama have been to do with Citta Siddhi.
Here we are concerned with Bhūta Siddha.
How does one obtain the ability to vanish?
Or as Vyāsa says not being seen, heard or smelled by anybody.
This implies that the Tanmātra of light, sound, smell etc… are checked and stopped so one can’t be seen.
Presumably singularly or collectively.”