The Egyptian Book of the dead by P. Le Page Renouf and Edouard Naville

4. Both the Eastern and the Western horizon are mentioned in this

chapter, but “Horus of the Two Horizons,” has no reference to this distinction. Whatever the Sun passes through or over is always conceived as double. The _Two Earths_ imply simply the Earth as divided by the passage of the Sun above it. It is to M. Grébaut that we are indebted for the discovery of this important key to many Egyptian expressions.