Mohamed's Footprint Marzouki

Embedded in the floor of the mihrab of Sidi Marzouki Mosque are two footprints said to be from the Prophet Muhammad. I couldn't find anyone with knowledge of where they came from, nor how they arrived in Cairo but many people say that when Muhammad walked across sand he didn't leave a mark, but when he walked across stone he left footprints. I found two other footprints of Muhammad in Egypt, one in the Sultan Qaitbay mosque in Cairo’s City of the Dead, and another in the Said Ahmed al-Badawy Mosque in Tanta.