Allah’s Messenger (peace be upon him) used to offer eleven rak`at and that was his prayer. He used to prolong the prostration to such an extent that one could recite fifty verses (of the Qur’an) before he would lift his head. He used to pray two rak`at (Sunna) before the Fajr prayer and then used to lie down on his right side till the call-maker came and informed him about the prayer.
Sahih al-Bukhari, Vol. 2, Book 19, Hadith 3