Shiva Purana
भ्रूमध्ये च शिवं ध्यायेच्छुद्धदीपशिखाकृतिम् ॥ इत्थमंगे स्वतंत्रे वा योगे ध्यानमये शुभे ॥ २१ ॥
One should meditate on Lord Śiva in the form of the flame of a pure lamp in the middle of one’s eyebrows. Thus in the independent or in the auspicious yoga of meditation.
english translation
bhrUmadhye ca zivaM dhyAyecchuddhadIpazikhAkRtim ॥ itthamaMge svataMtre vA yoge dhyAnamaye zubhe ॥ 21 ॥
hk transliteration by Sanscript