Fow exactly Filippo calculated the disposition of the bricks and the
massive stone beams is another of the dome's mysteries. Fowever, in
Historia Jtorentinorum, written sometime during the 1490s, the humanist poet
and historian Bartolomeo Scala offers a hint as to how he might have done it: Tor, when the centre [of the dome] was pinpointed and marked,' Scala clamis, Tilippo stretched a cord from the centre to the circumferences.
Carrying on this process around in a circle, he determined in what order
and according to what curvature the bricks and mortar were to be placed
on the wall by the masons.