Musannaf Ibn Abi Shayba 16:712

Abu Bakr narrated to us, he said: Ibn Adam narrated to us, he said: Husayn narrated to us, from Yazid ibn Abi Ziyad, who said: I saw the sandal of the Prophet, may Allah bless him and grant him peace, in Medina. It was tapered (at the waist), pointed, and had a protruding heel.