Toscanelli Dal Pozzo, Paolo

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(b. Florence, Italy, 1397; d. Florence, 1482)

astronomy, geography, medicine.

Toscanelli’s father, Domenico, was a physician. Information on Toscanelli’s work is scanty and incomplete, since only a few fragments of his writings are extant. He must have begun his studies in medicine, mathematics, and astronomy at the University of Florence but later transferred to the more famous University of Padua, where he formed a friendship with Nicolas of Cusa. While pursuing his medical studies at Padua, Tascanelli was drawn to astrology but nevertheless achieved important results in astronomy.

On his return to Florence, the Signoria of the city assigned Toscanelli the treatment of “judicial astrology,” then much in vogue. Deemed by Cusa and Regiomontanus as the most learned living mathematician, he was introduced to Brunelleschi, then busy with the construction of the large cupola of the basilica of Santa Maria del Fiore. The great height of the lantern above the cupola gave Toscanelli the idea of placing a gnomon there, the highest ever built. Very little information is available concerning this important astronomical instrument; but the testimony of Egnatio Danti, the cosmographer of Cosimo I de’Medici, states that Toscanelli pierced an opening at the base of the lantern, through which the rays of the sun passed. The purpose was to determine with accuracy the day of the solstice and other astronomical data. The opening is ninety meters above the floor, and at high noon during the summer solstice the sun’s rays fall on the marble floor of the basilica.

Stone slabs have been embedded in the floor at various times. The oldest, according to Ximenes, who in 1755 studied and reconstructed this meridian line, was the one that Toscanelli placed there in 1468.

Toscanelli also demonstrated his ability in astronomy through his observations of the comets that appeared in 1433, 1449, 1456, 1457, and 1472. (It was not until 1864 that his manuscripts in the National Library at Florence were discovered.) Although these observations were made without instruments, his methods of cartographic representation were much more accurate than those then in common use. In fact Giovanni Celoria (1842-1920), director of the astronomical observatory at Brera (Milan), was able to calculate the cometary orbits on the basis of Toscanelli’s drawings. Thus he ascertained that the comet Toscanelli observed in 1456 was the one now known as Halley’s comet.

Cristoforo Landino, professor of rhetoric and poetry at the University of Florence and a friend of Toscanelli, states that the latter held many conversations on geography with travelers and navigators who passed through Florence. It was probably as a result of these conversations that he decided to construct a nautical map of the Atlantic Ocean, even though knowledge of the longitudes of various places was then quite imperfect. Therefore it is not surprising that the positions of Cathay and of the island of Cippangu—that is, of China and Japan—were only vaguely known. They were placed more than one hundred degrees too far to the east, halfway between their correct locations and Lisbon, a displacement toward Europe of about ten thousand kilometers. The purpose of the map was to demonstrate that if one sails west, one can reach the Orient by a shorter route and thus circumnavigate the globe. Documents of the period indicate that the map, which was later reconstructed, was sent by Toscanelli with a letter to Fernando Martins, canon of Lisbon, whom he had met in Italy at the time of Cusa’s death. In the letter he demonstrated that it was possible to reach “the most noble and large city of Quinsay” (China) by crossing the Atlantic. At the end of his life, Toscanelli apparently sent a copy of his map to Christopher Columbus, urging him to use it for exploration.


Gustavo Uzielli, La vita e i tempi di Paolo dal Pozzo Toscanelli (Rome, 1893), contains an extensive bibliography and was reprinted in Pubblicazioni del R. Osservatorio astronomico di Brera, no. 55 (1921).

See also Carlo Errera, L’epoca delle grandi scoperte geografiche (Milan, 1926): G. Fumagalli, Bibliografia delle opere concernenti Toscanelli e Amerigo Vespucci (Florence, 1898); Hermann Wagner, “Die Rekonstruktion der Toscanelli Karte von Jahre 1474 und die PseudoFacsimilia des Behaim Globus v.j. 1492,” in Nachrichten der K. Gesellschaft der Wissenschaften zu Göttingen, Phil.-hist. Kl. (1894); and his review of H. Vigaud, “La lettre et la carte de Toscanelli sur la route des Indes par l’ouest . . .,” in Göttingischen gelehrten Anzeigen (1902), no. 2; and L. Ximenes, Del vecchio e nuovo gnomone fiorentino (Florence, 1757).

G. Abetti