Yahya related to me from Malik that Yahya ibn Said said, "I sawAnas ibn Malik on a journey praying on a donkey facing away from theqibla. He did the raka and the sajda by motioning with his head,without putting his face on anything." (IT)
USC-MSA web (English) reference: Book 9, Hadith 29 (IT)
Arabic reference (IT): Book 9, Hadith 358 (IT)