Shiva Purana
ब्रह्मजज्ञानम्प्रथममितिमंत्रेण मस्तके ॥ स्पृशञ्जप्त्वा रुद्रसूक्तं भुवोर्मध्ये स्पृशञ्जपेत् ॥ ५८ ॥
Brahmajajnanamprathamamiti mantra on the head. After chanting the Rudra Sukta, one should touch the middle of the earth.
english translation
brahmajajJAnamprathamamitimaMtreNa mastake ॥ spRzaJjaptvA rudrasUktaM bhuvormadhye spRzaJjapet ॥ 58 ॥
hk transliteration by Sanscript