Shiva Purana
शिवस्वभाव एवैकश्चिंत्यते निरुपाधिकः ॥ यथा शैवमनोवृत्तिर्महायोग इहोच्यते ॥ ११ ॥
Wherein the nature of Śiva is contemplated without any conditioning or restricting factor, the concentration of the mind on Śiva is called Mahāyoga.
english translation
zivasvabhAva evaikazciMtyate nirupAdhikaH ॥ yathA zaivamanovRttirmahAyoga ihocyate ॥ 11 ॥
hk transliteration by Sanscript