Yōga Sūtra 3.21

कायरूपसंयमात्तद्ग्राह्यशक्तिस्तम्भे चक्षुःप्रकाशासम्प्रयोगेऽन्तर्धानम्।

kāyarūpasaṁyamāttadgrāhyaśaktistambhē cakṣuḥprakāśāsamprayōgē'ntardhānam।

[काय रूप संयमात् तत् ग्रह्य शक्ति स्तम्भे चक्षुः प्रकाश असम्प्रयोगे अन्तर्धानम्।
kāya = physical body; rūpa = form; saṁyamāt = by samyama; tat = its; grahya = grasp; śakti = ability to; stambhē = suspending; cakṣuḥ = eye's; prakāśa = brightness; asamprayōgē = obstructing the contact; antardhānam = disappearance;]

By samyama of physical body form, suspending eye's ability to grasp, obstructing the contact of light with eyes, disappearance (of object) is achieved.