With computers then very slow, Hales and Ferguson used a highly optimized, heuristic-based program to check each case and show it was below approximately 0.74, the optimal packing ratio.

“Now, back in these days, computers were incredibly slow, so almost on a case-by-case basis, they had to write this insanely optimized computer program with lots of heuristics, doing intersection checking and so on, to individually prove that each one was less than about nought point seven four, which is the ratio of the optimum, uh, you know, pyramid placement.”