On the ceiling of the sepulchral chamber of the cenotaph of Seti I at Abydos and the tomb of Ramses IV in the Valley of the Kings was drawn a funerary composition known as the Book of Nut - the sky-goddess. This composition tells us about the daily journey of the Sun, from its going forth from Nut's vulva in the early morning as Khepri until its disappearance within Nut's mouth in the late evening in the form of a winged solar disk. Nut's vulva therefore can be seen as the daily rebirth place of the Sun. As a consequence, it designates the eastern horizon, whereas her face likely symbolizes the western horizon. The rest of her body certainly materializes the extension of the nightly journey of the Sun. Its daily journey is made between sky and earth, between Nut and Geb which the Air-god Shu separates. (12).

Ceiling of the sepulchral chamber of the cenotaph of Seti I (dynasty XX, Abydos)