Thanks, Ben Chorin, for the enlightening post.
I heard a few years ago (from someone who is 'holding' but, unfortunately, must remain nameless) that none other than Sir Isaac Newton wrote a massive tract on Biblical measures. As it turns out, his approximations are ridiculously close to those of the Chazon Ish!
As to how he arrived at those numbers, I have a theory:
Sir Isaac was sitting under a tree, contemplating the cosmos, when all of a sudden this MASSIVE olive fell and clunked him on the head...