Shiva Purana
एवं त्रिवारं संप्रोक्ष्य शिरसि त्रिः पिबेत्ततः ॥ समाहितेन मनसा ध्यायन्नोंकारमीश्वरम्॥ २९ ॥
Thus sprinkle three times on the head and then drink three times. Meditating on the Lord with a concentrated mind.
english translation
evaM trivAraM saMprokSya zirasi triH pibettataH ॥ samAhitena manasA dhyAyannoMkAramIzvaram॥ 29 ॥
hk transliteration by Sanscript