The author of the Ain-ul-Hayat was Ibn-i-Muhammad Hadi Muhammad Ismail. In Volume 2, Chapter 2, pages 177 to 178, he states the following regarding Yuz Asaf:
“He went to many cities and preached to those cities. At last he reached the city of Kashmir. He invited its inhabitants to righteousness and resided there till death approached him, and his holy spirit departed from his earthly body and went to rest with God. But before his death he called his companion Ba’bad and made a will…and directed him to construct a tomb for him. He laid himself with his head towards the East and stretched his legs towards the West, and went to the place of eternity.”
(Ibn-i-Muhammad Hadi Muhammad Ismail, Ain-ul-Hayat,Vol. 2, chapter 2, pp. 177 to 178).