Page 286 of your excellent book refers to the Muslim settlement and the modern mosque of Negash but does not mention the interesting tomb situated adjacent to the ancient Muslim graveyard (just behind the modern mosque). It is possible to visit the tomb if the guardian can be found. He will even pull back the outer coverings of the tombs of the “companions of the prophet” so that the rich inner coverings can be seen.
There are 7 graves in the graveyard. We were told these were graves of the original settlers. We were told that there were 20 original settlers, later followed by some 100 more. This grave looks recent, but we were told that the graves had been looked after and restored over the centuries. I don’t know how old the tomb building is, but we were told that the remains of “those closest to the prophet” were taken from the graveyard and placed inside the tomb at a later date. The tomb is therefore said to contain the remains of those closest to the prophet (I have no names) who are the most revered of the original refugees. As you say in your book, these were said to include Mohammad’s daughter Rukiya. It was not clear to me whether they were claiming that she was amongst those buried inside the tomb building.