Yōga Sūtra 1.20
श्रद्धावीर्यस्मृतिसमाधिप्रज्ञापूर्वक इतरेषाम्।
śraddhāvīryasmr̥tisamādhiprajñāpūrvaka itarēṣām।
[श्रद्धा वीर्य स्मृति समाधि प्रज्ञा पूर्वक इतरेषाम्।
śraddhā = keen interest with reverence; vīrya = bravery; smr̥ti = recalling past events with the intention of introspection; samādhi = equilibrium state; prajñā = knowledge; pūrvaka = accompanied with; itarēṣām = and others;]
Equilibrium state (samadhi) with knowledge and others is obtained by keen interest with reverence, bravery, and introspection.
For obtaining any equilibrium state keen interest with reverence, bravery and memory are stated as pre-requisite. Here smruti is to be understood to mean recalling past events with the intention of introspection.