Long before he became a curmudgeonly literary hero, it was
Mark Twain's job to
'mark twain' as he helped pilot steamboats on the Mississippi river. 2 fathoms or 12 feet was the minimum depth required for safe passage.
'Twain' denoted the second marking on a river measuring guide. He began life as Samuel Clemens, only adopting Mark Twain when he was more than thirty years old. Twain has the exceptional honour of being born and dying while Halley's Comet was visible from Earth.
Oh, East is East, and West is West, and never the twain shall meet,
Till Earth and Sky stand presently at God's great Judgment Seat;
But there is neither East nor West, Border, nor Breed, nor Birth,
When two strong men stand face to face,
tho' they come from the ends of the earth!
