Anyone can very easily comprehend this principle when manufacturing a scale. If one were to manufacture a mathematically perfect, symmetrical scale beam out of metal, as even as possible in density, and he would then balance it in a scale fork, he would find out that, even with such mathematically correct perfect proportions, the two scale beams, or rather the two parts of the same scale beam, will never form a perfect horizontal plane. But one part will be a little bit out of balance from the other, and the manufacturer of the scale will have to modify the scale beam on one side or the other with a file or hammer. The reason for this lies of course in the principle mentioned above. – The Earth, Chapter 1, Paragraph 5
