SB 4.8.31
munayah padavim yasya
nihsangenoru-janmabhih
na vidur mrgayanto ’pi
tivra-yoga-samadhina
Translation by His Divine Grace A. C. Bhaktivedanta Swami Srila Prabhupada:
Narada 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 yogis were unable to find the end of the path of God realization.