I received a humorous circular from a friend, arguing that one of the large-scale design features of the space shuttle derives from the gauge of the Roman wheel-rut, designed to accommodate the width of two chariot-horses. The punchline is "so horses' arses control everything."
A few minutes' Internet search traces the core of this message back to a 1994 posting: http://www.langston.com/Fun_People/1994/1994ADL.html (appended below for the record, lest it vanish; accessed 20120102).
I doubt very much that was the first year it appeared. But it's interesting to see how long these things propagate for. February of 1994 was just about the time I started using the Internet again, after a hiatus of 14 or 15 years. I have a vague recollection of having seen it around that time, and of remembering then that I had heard a school-buddy recounting something similar in the 1970s.
Version of 19940209:
> Date: Wed, 9 Feb 94 16:37:01 PST > >
Subject: UBPIOTD (Useless But Possibly Interesting Information Of The Day, natch)
From: Nat Howard
From: Bill Innanen
US Standard Railroad Gauge
How MilSpecs Live Forever
The US standard railroad gauge (distance between the rails) is 4 ft 8 1/2
in (1.44 m). That's an exceedingly odd number.
Why is that gauge used? Because that's the way they built them in England,
and the US railroads were built by English ex patriots.
Why did the English build 'em like that? Because the first rail lines were
built by the same people who built the pre-railroad tramways, and that's
the gauge they used.
Why did *they* use that gauge then? Because the people who built the
tramways used the same jigs and tools as they used for building wagons,
which used that wheel spacing.
OK! Why did the wagons use that wheel spacing? Well, if they tried to use
any other spacing the wagons would break on some of the old, long distance
roads, because that's the spacing of the ruts.
So who built these old rutted roads? The first long distance roads in
Europe were built by Imperial Rome for the benefit of their legions. The
roads have been used ever since.
And the ruts? The initial ruts, which everyone else had to match for fear
of breaking their wagons, were first made by Roman war chariots. Since the
chariots were made by or for Imperial Rome they were all alike in the
matter of wheel spacing (ruts again).
Thus we have the answer to the original question.
The United States standard railroad gauge of 4 ft 8 1/2 in derives from the
original military specification (MilSpec) for an Imperial Roman army war
chariot. MisSpecs [dpb: sic] (and bureaucracies) live forever!