The walls are comprised of five layers of blocks, each layer being 16 palms high. That makes the walls 80 palms (320 fingers) high.

The floor slabs are 1/4 cubit (7 fingers) high. Subtracting this gives the floor-to-ceiling height as 313 fingers.

Why 313 fingers?

Initially it would appear that the goal was to make the height of the chamber half the floor diagonal, the effect of this being to create a 2 x 1 rectangle across the vertical diagonal of the chamber, the same 2 x 1 design as the floor.

But again, why?

The effect of having a ceiling height of 313 fingers is to make the end wall diagonal 15 cubits and the cross-chamber diagonal 25 cubits. In combination with the 20-cubit floor length, this makes a 3-4-5 right triangle across one of the diagonals of the chamber. (I'm sure you've seen the diagram.)

Whoever devised this 3-4-5 configuration was a genius.

Our certainty that a 3-4-5 triangle of these dimensions was intended is increased by the discovery that Khufu's Mortuary temple is 75c x 100c, implying a 3-4-5 triangle exactly five times the dimensions of the 3-4-5 triangle expressed in the KC.

The only Egyptologist I know who has looked into the deeper meaning of this is Gyula Priskin. I concur with Priskin's claim to have discovered a calendrical system of measurement that uses sandals (= 1/6 cubit) and short cubits of 5 sandals. When the chamber's 3-4-5 triangle is rendered in sandals, it becomes 90-120-150. The perimeter of this is 360 sandals, the same number as days in the Egyptian civil year, and incidentally the same number as cubits in the base of the Bent Pyramid. When the mortuary temple's 3-4-5 triangle is rendered in short cubits, it also becomes 90-120-150.

The base of 75 x 100 cubits is again used as the ground plan of the mastaba of Ptahshepses at Abusir, the last structure built there.

A triangle of these dimensions (75-100-125 cubits) is used to make the profile or slope of the pyramids of Djedkare-Isesi, Teti, Pepi I, Merenre and Pepi II.

The number 360 represents the circuit of the sun, and thus this 3-4-5 triangle with the specific dimensions of 90-120-150 would come to be regarded as sacred because of its close association with the solar cycle.

Sahure's pyramid also fits into this calendrical symbolism. It has a base length of 150 cubits and height 90 cubits, giving it a slope of 6:5, or a seked of 5/6 cubit, the calendrical short cubit.

The first expression of this calendrical symbolism can be found in the Bent pyramid. Its base is 360 cubits, the sacred calendrical number. The core of the Bent pyramid has a base of 300 cubits, which can be rendered as 360 short cubits, again, the sacred calendrical number.

In fact it can be seen that Sahure gets the dimensions of his pyramid from those of the Bent pyramid. The height of Sahure's pyramid, 90 cubits, is taken from the height of the lower part of the Bent pyramid, i.e., the height to the bend, and one-quarter of its 360-cubit base. The base of Sahure's pyramid, 150 cubits, is taken from the semi-base of the core of the Bent pyramid.