Abdullah bin Hassan al-Anbari (may Allah have mercy on him) said: My two grandmothers, Safiyyah and Duhaybah, the daughters of Ulaybah (Musa bin Harmalah said: the two of them were raised in the care of Qaylah bint Makhramah (may Allah be pleased with her), and she was their father's grandmother), informed that she saw the Messenger of Allah (peace and blessings be upon him) sitting in the posture of al-qurfusa' (squatting). When I saw the Messenger of Allah (peace and blessings be upon him) (with utmost dignity) (and Musa said: he (peace and blessings be upon him) was humble and lowly in his manner of sitting), I trembled out of awe. Abu Ubayd said: Al-qurfusa' means that a man sits in the manner of one sitting with his knees drawn up (ihtiba'), placing his hands together on his shins, just as one draws up the knees with a cloth.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الجمعة / 5915