John Bright has kindly supplied this photo which he has asked me to post because of its possible relevance to ongoing discussions in the comments.
I took it [the photograph] at Karnak in November 2003. It is a block of calcite that had been unearthed in the north east corner of the First Court where the Bubastite Colonnade meets the Second Pylon. New lighting cables had been laid and this block was awaiting removal to a storage area. Though battered, the cartouches of Akhnaten and the Aten can be seen. The water bottle at the base is 15cms in height so it gives scale to the block which is clearly more substantial than a talatat. At an educated guess, I would say it was part of an offering table as a cornice appears to have been trimmed off.Image © John Bright