In 1550 Vasari wrote about Leonardo: «And among all these models and drawings there was one which he showed several times to the many intelligent citizens then ruling Florence, to demonstrate how he wanted to raise the church of San Giovanni and place steps under it without destroying it; and he persuaded with such good reasoning that they thought it possible, even though, upon leaving him, each of them realised the impossibility of such an undertaking.»
In reality, Leonardo's project already had precedents. A few years earlier, in 1455, the Bolognese engineer and architect Aristotile Fioravanti (c. 1415-1486) had successfully moved a tower in Bologna, with the aid of rollers, beams and jacks. Fiorovanti had also worked for some of Leonardo's friends and clients, such as the Bentivoglio family, King Mattia Corvino of Hungary and Cosimo de’ Medici (between 1458 and 1467 in Florence).
Leonardo's project called for raising the Baptistery on four steps, as can be seen in a drawing attributed to Francesco Granacci (now in the Uffizi Cabinet of Drawings and Prints) and in two replicas of the Baptistery ("Ancient temple of Mars, today of St. John") published in the Discorsi [Discourses] of Vincenzo Borghini (Florence, Giunti, 1584). The model was rebuilt in 2007 and is displayed today at the Museo del Bigallo in the "Leonardo in Florence" section.