The success of Brunelleschi's enterprise rested on two major factors: the efficient organization of the worksite, and the availability of efficient machinery such as lewises, turnbuckles, and devices for lifting massive weights. Brunelleschi designed machines for the individual operations, but left no drawings or written descriptions of them. Our only evidence is the illustrations by Taccola, Francesco di Giorgio, Giuliano da Sangallo, Bonaccorso Ghiberti, and the young Leonardo.