Columbus's father-in-law had himself been the Portuguese governor of the
island of Porto Santo, where he had founded a colony. He, therefore,
was interested in western explorations, and probably from him Columbus
collected some of the statements which are known to have influenced
him, with regard to floating matters from the West, which are constantly
borne upon that island by the great currents of the sea.

The historians are fond of bringing together all the intimations which
are given in the Greek and Latin classics, and in later authors, with
regard to a land beyond Asia. Perhaps the most famous of them is that of
Seneca, "In the later years there shall come days in which Ocean shall
loose his chains, and a great land shall appear . . . and Thule shall
not be the last of the worlds."

In a letter which Toscanelli wrote to Columbus in 1474, he inclosed a
copy of a letter which he had already sent to an officer of Alphonso V,
the King of Portugal. In writing to Columbus, he says, "I see that you
have a great and noble desire to go into that country (of the East)
where the spices come from, and in reply to your letter I send you a
copy of that which I addressed some years ago to my attached friend in
the service of the most serene King of Portugal. He had an order from
his Highness to write me on this subject. . . . If I had a globe in
my hand, I could show you what is needed. But I prefer to mark out the
route on a chart like a marine chart, which will be an assistance to
your intelligence and enterprise. On this chart I have myself drawn the
whole extremity of our western shore from Ireland as far down as the
coast of Guinea toward the South, with all the islands which are to be
found on this route. Opposite this (that is, the shores of Ireland and
Africa) I have placed directly at the West the beginning of the Indies