Yōga Sūtra 2.51

बाह्याभ्यन्तरविषयाक्षेपी चतुर्थः।

bāhyābhyantaraviṣayākṣēpī caturthaḥ।

[बाह्य अभ्यन्तर विषय आक्षेपी चतुर्थः।
bāhya = outside; abhyantara = inside; viṣaya = topic; ākṣēpī = is beyond; caturthaḥ = the fourth;]

That which is beyond the subject of outside, and inside (suspension of prāna) is the fourth.