When I read “The Royal Arch Its Hidden Meaning” by George Steinmetz I was surprised by the esoteric content of the last two chapters of this well written book. While there is not enough space here to go into much detail I thought I would share the opening paragraphs of Chapter VI for your comments.
It is when the COMPLETE MAN, whom the "three weary sojourners" represent, reaches his destination "Jerusalem" and stands at the entrance of the Tabernacle seeking admission, that the most profound Occult Philosophy is introduced into this degree.
All through the Masonic degrees the numbers "four" and "three" are encountered. They are most frequently symbolized by the square and triangle, or compasses, which derive from the triangle. This is true of the apron as well as the square and compasses themselves. The square and triangle are two of the oldest symbols known to humanity and are strictly astrological signs. Without some knowledge of astrology it is impossible for anyone to fully understand the symbology of the Royal Arch degree, or for that matter Freemasonry, for it is replete with astrological references.
I am prompted to make a deliberate digression at this point. I am impressed with the many times it has appeared necessary to remark: "Without some knowledge of (some other subject) it is impossible to fully understand etc." How many, many times in any Masonic discussion this occurs. It forcefully reminds one of the seven steps of the Symbolic Lodge, likened to the seven liberal arts and sciences. It reminds one of the universality of Freemasonry and the need of being conversant with all other sciences if one expects to understand the profound truths taught by Masonic Philosophy. There are still other interpretations of these seven steps and at least one other will be apparent to the reader as we progress now that the steps have been called to his attention. He may also be prompted to make some applications for himself and discover additional ones.
The theory that the earth is flat and square and the heavens a great inverted dome, is attributed to the ancients. The earth being material it was natural to adopt the square as the symbol of the earth, and eventually it came to be used as a symbol for all material things including material, or physical man. As triangulation is used in measuring spheres, a sequence of reasoning is that the "Heavens" are spherical; they are the abode of the gods; the gods are spiritual, hence a triangle symbolizes heaven, Deity and things spiritual, including spiritual man.