(a) Sayyiduna Amir bin Abdullah bin al-Zubayr (may Allah have mercy on him) narrates from his father (may Allah be pleased with him) that he said: I saw the Messenger of Allah (peace and blessings be upon him) supplicating like this; then he placed his hands on his knees and sat cross-legged.
(b) Imam al-Bayhaqi (may Allah have mercy on him) said: Uqbah (may Allah have mercy on him), the brother of Sa'id bin Ubayd al-Ta'i (may Allah have mercy on him), said that he saw Sayyiduna Anas bin Malik (may Allah be pleased with him) praying while sitting cross-legged.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الصلاة / 3663