Kurmapurana 2.11.42

Kūrmapurāṇa 2.11.42

dhāraṇā dvādaśāyāmā dhyānaṃ dvādaśadhāraṇāḥ /
dhyānaṃ dvādaśakaṃ yāvat samādhirabhidhīyate //