Re: Le Grand K's fate
"They did use the 10.000 km as the distance from the equator to the pole by simply saying it's 10.000 and thus 1m is what it is."
For some reason the metre was defined as 1/10,000 of 1/4 of the circumferential arc a few times in history.
The French innovation seemed to be defining it from pole to equator (of course that's going to be different from north pole vs south pole, oblate spheroid etc). Previous definitions were either at the equator or sliced at the latitude of the city of the civilisation which defined it - so the egyptian metre was slightly longer than the greek metre, etc (the ancients were perfectly well aware that the earth was round and had a pretty accurate idea of its size. Colombus' fallacy was that it was much smaller than it is and everyone thought he'd starve to death on the voyage, not fall off the edge. He nearly did starve too - and falsified ship's log records to make it seem as if the distance travelled was considerably less than reality in order to deceive his crew, because by his stated original calculations they should have reached Asia long before they hit the Carribean.)
The roman mile was slightly different, being "1000 marching paces" and defined to allow for planning of rest breaks, etc.