Musnad Ahmad 28:328

Yahya ibn Sa'id narrated to us, from al-Taymi, from Aslam, from Abu Murayyah, from the Prophet (peace be upon him), or from Abdullah ibn Amr, from the Prophet (peace be upon him), who said: "The two blowers are in the second heaven; the head of one of them is in the East and his feet are in the West," or he said: "The head of one of them is in the West and his feet are in the East. They are waiting for when they are commanded to blow into the Trumpet, so they will blow."