The Flagellation of Christ
Disclaimer: Please note that my perspective is aesthetic inspiration, practicality and real life theoretical implications rather than mathematical.
I know it's very risky to try to apply some geometrical formula on a piece of art. I'm an artist myself and it's always a lot of other consideration when working with an artistic sense other then trying to conform to a single strict geometrical formula. But let's do this exercise just for fun. I leave it up to you to draw your own conclusions. The painting that is used in this example is "The Flagellation of Christ" by Piero della Francesca. The painting is to be found in the Galleria Nazionale delle Marche in Urbino, Italy.
The dimension of the painting is 58.4 cm × 81.5 cm. I'm not sure if this is the original size but the ratio of the painting is about 1:1.4.
It is clear that he is using some sort of central perspective to give the illusion of perspective.
Since the ratio of the painting is close to 1.4 I thought it would be fun to try looking at the painting from a root rectangle perspective (you can read more about root rectangles here). The number 1.4 is close to √2 so I will try to use a square root of 2 rectangle in my analysis.