But this doesn't really contradict the myth. You certainly can have rail gauges that are _smaller_ than two horses' asses. You don't _have_ to use all the available width all the time.

It's the lack of something significantly larger that matters for this myth.

> Hence the long distance railways often use exactly the same gauge - but the exact measurement was a matter of Parliament deciding on what compromise to draw based on early railway lines, bearing in mind that it was a lot easier to reduce gauge rather than increase it.

The Russian railway was specifically designed to be incompatible with others (it's slightly larger) to make it harder for invading forces to use it. But even then it was not that much different from others.