The mural at the end of the short little hallway is the key to solving the gods puzzle on the first sarcophagus. Take a picture of it with your cell phone, because obviously you can't take it with you.
How do I solve the gods puzzle on the coffin?
In addition, there's a piece of paper in the sand that makes interesting reading, as well as being useful in other ways. You'll find more of this journal as you move through the game.