Shiva Purana
महदेवश्च रेखायाः प्रथमायाश्च देवता । विज्ञेया मुनिशार्दूलाः शिवदीक्षापरायणैः 1-24-९० ।
Mahādeva is the deity of the first line.O foremost among sages, this shall be carefully understood by those who are initiated in the cult of Śiva.
english translation
mahadevazca rekhAyAH prathamAyAzca devatA । vijJeyA munizArdUlAH zivadIkSAparAyaNaiH 1-24-90 ।
hk transliteration by Sanscript