“The surface of the Great pyramid, about 5.25 acres per side, was originally covered by smooth white limestone. These casing stones, the edges of which are straight to within 1/100 of an inch over a distance of 75 inches, are also fitted to each other with uncanny precision. The joints between the stones average 1/50 of an inch in width and yet there is an extraordinarily thin film of white cement between them that bonds the blocks together. The average weight of these casing stones is sixteen tons, yet the precision with which they were laid has been compared to the work of an optician on the scale of acres. Some authors have speculated that these highly polished limestone sides of the Great Pyramid made it visible from the moon when the sun’s rays reflected from its surface. These stones were removed in the fourteenth century to build palaces and mosques in Cairo. A few of the original casing stones remain on the North side of the Great Pyramid and on top of the second pyramid.”

—John Van Auken