Shiva Purana
धारणा द्वादशायामा ध्यानं द्वादशधारणम् ॥ ध्यानद्वादशकं यावत्समाधिरभिधीयते ॥ ६० ॥
Dhāraṇā extends upto the twelve-petalled lotus of the heart. Dhyāna is the fixation of the Dhāraṇā in the twelve-petalled lotus. When Dhyāna extends to the twelve-petalled lotus it is called Samādhi.
english translation
dhAraNA dvAdazAyAmA dhyAnaM dvAdazadhAraNam ॥ dhyAnadvAdazakaM yAvatsamAdhirabhidhIyate ॥ 60 ॥
hk transliteration by Sanscript