It is narrated from Sayyiduna Abdullah bin al-Zubayr (may Allah be pleased with them both) that he saw the Messenger of Allah (peace and blessings be upon him): when he (peace and blessings be upon him) prayed and sat after two or four rak'ahs, he would place his left hand on his left thigh and his right hand on his right thigh, and point with the finger next to the thumb.
Hadith Referenceالمعجم الكبير للطبراني / باب العين / 13837