Musannaf Ibn Abi Shayba 1:277

Waki’ and Ishaq al-Razi narrated to us, from Ibn Abi Dhi’b, from Qariz ibn Shaybah, from Abu Ghatafan, from Ibn Abbas, who said: The Messenger of Allah (peace and blessings of Allah be upon him) said: "Perform *istinshaq* (sniffing water into the nose) twice, thoroughly, or three times." And Waki’ said: "Perform *istinthar* (blowing water out of the nose)."