Sutra 3.21

कायरूपसंयमात् तद्ग्राह्यशक्तिस्तम्भे चक्षुःप्रकाशासंप्रयोगेऽन्तर्धानम्॥२१॥

kāya-rūpa-saṁyamāt tat-grāhyaśakti-stambhe cakṣuḥ prakāśāsaṁprayoge-‘ntardhānam ॥21॥

kaaya=of the body; rUpa=form; saMyamaat=by performing samyama; tat=that; graahya=to be grasped or known; shakti=power; stambhe=on obstruction; chakShuH=eye; prakaasha=light; asaMprayoge=on absence of contact; antardhaanam=invisibility

Sw. Satchidananda

By samyama on the form of one’s body, [and by] checking the power of perception by intercepting light from the eyes of the observer, the body becomes invisible.

Bryant

By performing samyama on the outer form of the body, invisibility [is attained]. This occurs when perceptibility is obstructed by blocking contact between light and the eyes.

Taimni

By performing Samyama on Rupa (one of the five Tanmatras), on suspension of the receptive power, the contact between the eye (of the observer) and light (from the body) is broken and the whole body becomes invisible.

Aranya

When Perceptibility Of The Body Is Suppressed By Practicing Samyama On The Visual Character, Disappearance Of The Body Is Effected Through It’s Getting Beyond The Sphere Of Perception Of The Eye.