It is known, at least, that they were acquainted at the time the learned doctor wrote Columbus, in 1474, and it does not require a stretch of the imagination to fancy them together, and wondering what effect that letter would have upon a man who entertained views similar to their own. Columbus, it is thought, had then been pondering several years over the possible discovery of land, presumably the eastern coast of India, by sailing westward. "It was in the year 1474," writes a modern historian, "that he had some correspondence with the Italian savant, Toscanelli, regarding this discovery of land. A belief in such a discovery was a natural corollary to the object which Prince Henry of Portugal had in view by circumnavigating Africa, in order to find a way to the countries of which Marco Polo had given golden accounts. It was, in brief, to substitute for the tedious indirection of the African route a direct western passage--a belief in the practicability of which was drawn from a confidence in the sphericity of the earth."[4]
Later in life Columbus seems to have forgotten his indebtedness to Toscanelli, and "grew to imagine that he had been independent of the influences of his time," ascribing his great discovery to the inspiration of one chosen to accomplish the prophecy of Isaiah. But the venerable Florentine had pondered the problem many years before Columbus thought of it. "Some Italian writers even go to the extent of asserting that the idea of a western passage to India originated with Toscanelli, before it entered the mind of Columbus; and it is highly probable that this was the case."
There is this in favor of Toscanelli: He was a learned man, while Columbus was comparatively ignorant. He was then advanced in years, and had given the greater portion of his life to the consideration of just such questions, having had his attention called to them by reading the travels of Marco Polo and comparing the information therein contained with that derived from Eastern merchants who had traded for many years in the Orient. He was not a sailor, nor a corsair--though Columbus had been both, and had followed the sea for years--but he was an astronomer, and he knew more of the starry heavens, as well as of the earth beneath them, than any other scientist alive. "It was Toscanelli who erected the famous solstitial gnomon at the cathedral of Florence." For his learning he was honored, when but thirty years of age, with the curatorship of the great Florentine library, and for nearly sixty years thereafter he passed his days amid books, charts, maps, and globes.