Reply to post: 2 horse's arses is the legacy metric.

2 horse's arses is the legacy metric.

3.7m is the largest diameter rocket body that will fit down a single railroad tunnel. The dimensions of which are built around the standard rail gauge of 4' 8.5". Early rail cars were built on the same jigs as horse drawn wagons. Wagon wheel spacing was dictated by the ruts Roman chariots wore into Roman roads. Roman chariots were built to be drawn by 2 horses.

http://www.astrodigital.org/space/stshorse.html