"In the two pictures occupying the center of the ceiling, each of which is four braccia wide, are the celestial signs; these can be thrown back by means which cannot be perceived; and in a space representing the concave are to be two large spheres, one representing the earth: this will be made to descend by a concealed windlass, and will then be balanced on a support adequate to that purpose, so that when fixed, all the pictures and the maps on the cabinet will be reflected therein, each part being thus readily found on the sphere. On the other globe the forty-eight celestial signs will be arranged, in such sort that all the operations of the astrolabe may be performed most perfectly by the aid thereof. The plan of this work has proceeded from the Duke Cosimo, who desired to have all these parts of the earth and heaven brought for once fairly together in their just positions, exactly and without errors, to the end that they might be observed and measured, either apart or all together, as might be desired by those who study and delight in this most beautiful science. I have therefore thought myself bound to make a memorial of the same in this place, for the sake of Fra Ignazio; and that his ability, with the magnificence of that great Prince, who has judged us worthy to enjoy the benefits of so honorable a labor, may be made known to all the world."[315]