Amongst his writing I came across the following, which I will note.
Isosceles triangle; If such a triangle, it is found that it's sides run through the stones forming the rear walls of all four lateral chambers, and that three of the stones involved (Nos. 10,27,33) are coincident in angle with the triangle's sides. The fourth (no.15) only slightly divergent. The west chamber (at the head) falls symmetrically within the converging sides, its rear wall being 20 feet from the apex.
Such an agreement between the structures and a geometrical figure strongly suggests that the basic plan was in fact laid out in these terms. Further symmetry in plan is shown by the regular tilt of the axis of the lateral chambers westward from a line at right angles to the passage axis by 15 to 20 degrees. It is clear that some kind of regular plan was envisaged, presumably to definite units of measurement and with a knowledge of ratios, and that building followed this plan so far as practical difficulties in handling large masses of stone allowed.
As my maths is so terrible, I vaguely understand the above, to believe of course the theory that there is a mathematical sum to be had from the moving of stones is more difficult.
East Kennet Long barrow