Convert from mark twain to ch'ih [China]

Unit Definition (mark twain)
The mark twain or 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 (ch'ih [China])
The ch'ih is a unit of distance used in China during the colonial period. The ch'ih equals 10 t'sun, 35.814 centimeters, or 14.1 inches. There are 1800 ch'ih in a li.