prayatnaśaithilyānantasamāpattibhyām [YS 2.47]

bhavatīti vākyaśeṣaḥ prayatnoparamāt sidhyaty āsanaṃ yena nāṅgamejayo bhavati. anante vā samāpannaṃ cittam āsanaṃ nirvartayatīti.