SB 4.8.31

munayaḥ padavīṁ yasya
 niḥsaṅgenoru-janmabhiḥ
na vidur mṛgayanto ’pi
 tīvra-yoga-samādhinā
Synonyms: 
munayaḥ — great sages; padavīm — path; yasya — whose; niḥsaṅgena — by detachment; uru-janmabhiḥ — after many births; na — never; viduḥ — understood; mṛgayantaḥ — searching for; api — certainly; tīvra-yoga — severe austerities; samādhinā — by trance.
Translation: 
Nārada Muni continued: After trying this process for many, many births and remaining unattached to material contamination, placing themselves continually in trance and executing many types of austerities, many mystic yogīs were unable to find the end of the path of God realization.