«Remember the soldering with which the sphere of Santa Maria del Fiore was soldered. Of copper hammered to create a pebbled effect on the triangles of the globe.» In this note, which appears in Ms. G (f. 84v) and can be dated towards the year 1515, Leonardo recalls one of his first direct experiences with the practical applications of technology, when he stood alongside his teacher Andrea del Verrocchio on 27 May 1472 watching the work on the globe that was to surmount the lantern on the dome of the Cathedral of Florence, the crowning feature of Brunelleschi’s architectural masterpiece. No less than 4,383 libbre of copper went into the globe’s making, but this meant that it suffered damage on various occasions during storms, as described by chroniclers of the time. Finally, in the month of January 1601 a lightning bolt struck the lantern and the immense sphere fell to the ground. It was repaired and finally put back in place on 12 October 1602. On the eastern side of the Piazza del Duomo one can still see the white marble plaque that was embedded in the pavement to mark the exact site where the globe landed.
Leonardo also studied the macchina da collare (a lifting machine) that was used to reconstruct the lantern on the dome – a rotating crane based on an idea by Brunelleschi, which could stand on its own on the wall that was being constructed.