When I was an apprentice in 1960 I had to file a 1 inch brass cube with nothing but a file and a pair of bow calipers from a piece of round bar.
It had to be to size, and the same in all dimensions. At the end of my apprenticeship, I had to file a 1 inch sphere, with nothing but a file, a pair of bow calipers, and some cigarette papers. It had to be to size as well. I was chastised as the sphere was about .003 oblate...