What is a megalithic yard and how is it derived?

Question

and I'm not talking about the place where cavemen kept their bicycles.

Answer 1

Indeed!

He shouldn't be out on his own!

Answer 2

The relation among the units of length can be explained by the ratio 15:16:17:18 among the four fundamental feet and cubits. Before I arrived at this discovery, Decourdemanche and Oxé discovered that the cubes of those units are related according to the conventional specific gravities of oil, water, wheat and barley....... and of course the length of Fluffins.