No valid reason can be found other than the desire to institute, by the side of the common cubit in which the 6 palms and 24 digits corresponded to the watches and hours of the day, a sacred cubit in which the 7 palms would correspond to the seven planets or to the week of seven days, and the 28 digits to the vulgar lunar month of four weeks of seven days.[2] Among us, at the present day, astrology is far from being dead; the days still bear the names of the seven planets ruling successively the first hour of the days named respectively after them; we call, however unconsciously, men’s temperaments or characters according to the mercurial, jovial, saturnine and other influences of the planets which rule the hour of birth. It is not for us then to criticise severely the pious desire of a learned priesthood or of a theocratic king to institute a sacred standard of linear measure with divisions corresponding in number to the seven planets which ruled the destinies of man, whose influence ruled them through the Christian middle ages, which at the present day still rule the world in the minds of the great majority of mankind. The royal or sacred cubit became the official cubit of the Eastern great kingdoms, the common or meridian cubit being also used, not only for ordinary purposes, but sometimes along with it. Thus, the external dimensions of the Great Pyramid are in common cubits, while the unit of its internal dimensions is the royal cubit, perhaps recently established at the time of the building.[3] And centuries after the institution of the royal cubit, the meridian cubit became the standard of the Greeks. Footnote 2: Plutarch speaks of the mystic connexion assumed by the Egyptians between the 28 cubits maximum rise of the Nile and the same number of days in the lunar month. Footnote 3: The royal cubit is sometimes called the Philiterian cubit; this name (apparently meaning ‘royal’) is used by the later Hero of Alexandria, who wrote about 430. But Herodotus says, ‘They call the pyramids after a herdsman Philition who at that time grazed his herds about that place’; so it is probable that the name came from some legend. The question naturally arises—Why was the royal cubit not formed by simply adding a seventh palm to the common cubit, a palm of the same length, = 3·04 inches, as the six others? This would have given a new cubit of 18·24 × 7/6 = 21·28 inches, instead of 20·64 inches in 7 palms of 2·95 inches. And it will be seen that this was actually done, fifty centuries later, by the caliph Al-Mamūn. The answer I venture to give is, that the royal cubit was intended to be, not only by its division a homage to the seven planets, but also, by its increase of length, a symbol of the proportion of latitude to longitude at some Egyptian observatory.