Convert from twain to mile [international]

Unit Definition (twain)
The twain is an old word for the number two, derived from the Anglo-Saxon twegen. The American author Samuel Clemens (1835-1910), who had been a riverboat pilot on the Mississippi in his youth, took his literary name from a traditional riverboat phrase "mark twain", meaning "exactly two" fathoms of water. This was the minimum depth needed for the boats to operate safely without running aground.

Unit Definition (mile [international])
The mile is one of the most common measurements of distance. It originates from the Latin word for 1000, 'mille'. Originally a mile was the distance a Roman legion could march in 1000 paces. In medieval Britain, several mile units were used, including the modern mile defined as 8 furlongs (1609 meters). Note that French, Scottish and Irish miles varied from the English. In 1592, Parliament defined the statute mile to be 8 furlongs or 1609.344 meters.