 Later he is said to have met an old meditation master, known only as "White Head", who worsted Dharmakṣema in a debate that lasted ten days.He was given a copy of the Nirvāṇa Sūtra by the old monk and this is reported to have been the trigger of his conversion to Mahāyāna.He then studied Mahāyāna and by the age of twenty, he is said to have memorized a phenomenal amount of scripture.