Sir John Herschel, in his _Outlines of Astronomy_, thus shows the
changes in the celestial pole in 4000 years:
At the date of the erection of the Pyramid of Gizeh, which precedes
the present epoch by nearly 4000 years, the longitudes of all the
stars were less by 55° 45′ than at present. Calculating from
this datum the place of the pole of the heavens among the stars,
it will be found to fall near α Draconis; its distance from that
star being 3° 44′ 25″. This being the most conspicuous star in
the immediate neighbourhood, was therefore the Pole Star of that
epoch. The latitude of Gizeh being just 30° north, and consequently
the altitude of the North Pole there also 30°, it follows that
the star in question must have had at its lowest culmination at
Gizeh an altitude of 25° 15′ 35″. Now it is a remarkable fact,
that of the nine pyramids still existing at Gizeh, six (including
all the largest) have the narrow passages by which alone they can
be entered (all which open out on the northern faces of their
respective pyramids) inclined to the horizon downwards at angles
the mean of which is 26° 47′. At the bottom of every one of these
passages, therefore, the Pole Star must have been visible at its
lower culmination; a circumstance which can hardly be supposed
to have been unintentional, and was doubtless connected (perhaps
superstitiously) with the astronomical observations of that star,
of whose proximity to the pole at the epoch of the erection of
these wonderful structures we are thus furnished with a monumental
record of the most imperishable nature.