Jakob Burckhardt, in The Civilization of the Renaissance in Italy declared Petrarch a truly modern man, because of the significance of nature for his receptive spirit; even if he did not yet have the skill to describe nature. Petrarch's implication that he was the first to climb mountains for pleasure, and Burckhardt's insistence on Petrarch's sensitivity to nature have been often repeated since. There are also numerous references to Petrarch as an alpinist, although Mont Ventoux is not a hard climb, and is not usually considered part of the Alps. This implicit claim of Petrarch and Burckhardt, that Petrarch was the first to climb a mountain for pleasure since antiquity, was disproven by Lynn Thorndike in 1943.