Convert from point [Britain, US] to mark twain

Unit Definition (point [Britain, US])
The unit of measure for the height of type, defined as 1/72 of an inch* or 0.3527777778 mm (*small differences occur in this unit between countries, the variables lying between 0.188 and 0.4mm)

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.