The safe method which they illustrate may be described as follows.

You first take a model in wax or some other hard material, and place it lying in a vessel full of water.

The water, by its nature, presents a level surface; so that, if you gradually lift the model, the higher parts are first exposed, while the lower parts remain submerged; and, proceeding thus, the whole round shape at length appears above the water.

Precisely in the same way ought statues to be hewn out from the marble with the chisel; first uncovering the highest surfaces, and proceeding to disclose the lowest.

This method was followed by Michelangelo while blocking out the Captives, and therefore his Excellency the Duke was fain to have them used as models by the students in his Academy.