... or 'finitorium', depending upon which translation of On Sculpture you are reading. The illustration shows the disk, the boom arm, and the plumbline, which triangulate the position of any point on the surface of a statue.
Thomas Jefferson - Gutzon Borglum
This is the plaster cast of the face of Thomas Jefferson, from which sculptor Gutzon Borglum carved one of the faces of the Mount Rushmore National Memorial in South Dakota. Attached to the top of the model, we can see a diffinitore - disk, boom arm, and plumbline - that Borglum used to transfer point from the model to the mountain.
Gutzon Borglum's Diffinitore
Leon Battista Alberti describes this very device in the 1430's, to be used to transfer measurements from a mode lto the final marble sculpture. Here we see a diffinitore built in the 20th century for the same purpose, to assist in carving the Mount Rushmore National Monument.
Diffinitore in Use
Here we see a demonstration of a diffinitore I made, used to locate the point of an elbow from a sculpture.
I am using two sets of compasses to locate the nose of a sculpture from two known points. When combined with a third measurement from another known location, I can use these three measurements to describe the location of the nose - known as triangulation.
Pointing a relief
This is an illustration from Edauard Lanteri's 'Modeling and sculpting the human Figure'. T-squares and rulers are used to determine the height, width, and depth measurements on a relief. This is another way to triangulate points on the surface of a model.
The Pointing machine
A pointing machine, or macchinetta a punto, is made of a needle, attached to an adjustable arm, which sits upon a tripod. You position the needle to touch the surface of the model, then transfer the entire macchinetta and tripod to the stone, where the needle now points to the area of marble in which the point is to be found.
macchinetta a punto
A simple device consisting of a needle at the end of an adjustable arm.
The Chassis system
An illustration taken from Edauard Lanteri's "modeling and sculpting the Human Figure'. the chassis system of enlarging and pointing shows a framework built around the scale model and the enlargement. Each side of each frame is graduated like a ruler ,to their respective scales. In the image we can see an assistant transferring a measurement from the small model to the enlargement.