For which cause men may well perceive that the land and the sea are of round shape and form,

For which cause men may well perceive that the land and the sea are
of round shape and form, for the portion of the firmament that shows
itself in one country does not show itself in another country. And
men may well prove by experience and subtle exercise
of wit that if a man should find routes by ship that would go
to search the world, men might go by ship all about the world and
around and beneath it...
-- Sir John Mandeville,
-- Mandeville's Travels, a 14th-Century text of disputed authorship