In Leonardo DaVinci’s famous painting “The Last Supper”, he seems to have painted a table that should by all rights not be able to stand. There are 4 trestles along the front, and nothing supporting the back. This seems surprising given DaVinci’s knowledge of mechanical things. What gives? Is there a good story behind this?
While we’re at it, is there any truth to the story that the model for Judas was, to DaVinci’s surprise, the same person who had posed 7 years earlier as the model for Jesus?
Realistic perspective is not all that common in the old masters. To paint with realistic perspective you need a vanishing point where all real world parallel lines meet. You would need to plan for this, and clearly DaVinci didn’t in this case.
As to your second question, that is another ridiculous urban myth that’s been floating around the net recently. It was addressed in a recent GQ forum.
The Judas-as-Jesus story has been discussed at least twice before on the SDMB. The earliest thread is http://boards.straightdope.com/sdmb/showthread.php?threadid=3461
The reason that the table doesn’t fall is, it’s not really at table at all. It is just a picture of a table.
Look, it’s JESUS sitting at the table. Of course it’s not gonna fall. The guy can walk on water.
And that painting DOES have converging perspective. That has nothing to do with the table, though. Most “old” masters used perspective after about 1460 or so, in some manner (it wasn’t the monolithic Truth we now think of it as).
In answer to the OP - Divine Intervention, maybe? 
It was, after all a religious painting. (I can’t recall - was it a Papal commission? probably thinking of Micheal Angelo).
Once upon a time, I was intrigued by the whole Copernicans (Galileo as whipping boy) vs Jesuits deal. It is an interesting thing to think of: What to do when what mama told you just don’t jibe with your observational data?
The remaining table legs were removed when daVinci painted out the Kangaroo and the other two Christs.
I like the Kangaroo response…but…going back to the initial response…
I don’t think its due to inability to deal with perspective on DaV’s part. Peoples’ legs are clearly visible at the back/underside of the table, where the other trestle legs ought to be…and the people legs are not just blocking the view of the table legs.
But thanks for all the creative answewrs so far (and any more!)
Bob K.
picmr
I just looked at the picture. There is a vanishing point. It is Jesus’s head. (Where else?)
The only pictures I’ve seen (so far) are so bad, I can’t tell what’s going on under the table, but it looks to me like the supports go from front to back and would support the table top.
Paint’s just not that heavy.
It’s a painting of a table. It doesn’t have to actually be a table, it just has to read “table.” The focus of the painting is the figures and that was what Leonardo concentrated on - the faces, the gestures, the emotions.
Leonardo da Quirm’s Feast of the Turtle is very similar but his painting is only of feet and table legs - it’s the one part of the body he felt he really did well.
Poor da Vinci. He was commissioned to paint The Last Supper on a plaster wall. Said plaster immediately sucked up the paint, leaving but a faint copy of da Vinci’s vision. Then, several years later, the monks decided they needed a new door. So they knocked away part of the bottom center of the painting. I understand restoration of the painting is in progress, though. The table is probably being held up by the accumulated guilt of those blaspheming monks.
Here’s a real challenge for ya: Who’s driving the train down the chimney in Salvador Dali’s painting?
As M.K. pointed out, it is Jesus sitting at the table. Being a carpenter who could do miracles, he probably built it himself.
Why is everyone sitting on the same side of the table? :D:D
Why are their french table lighters on the table?
Why is there fluffy Italian-style bread, obviously made with yeast, when this is supposed to be a Passover Seder???!!!
Oh, and they’re all on one side of the table 'cause the photographer said, “Anyone who wants to be in the picture, squeeze in over there.”
Blasphemy? The monks did PAY for the painting and if they needed to put a door there, it was presumably to better accommodate the monastic life. As for the plaster bit, painting on plaster al fresco was a very well understood and ancient technique. Leonardo was experimenting with some new paint formulations, as was his habit, however - and this did cause all sorts of trouble in the early years. The real disintegration came later with vandalism and, more importantly, the combined effects of millions of gawkers who were less breathless in the shadow of the masterpiece than maybe they should have been. Our own exhalations are the only blasphemy against the work, depending on your view toward conservation…
Yes, fresco secco was common-- Leo just happened to think it a good idea to experiment with a different sort of paint-- perhaps a type of oil paint, instead of the usual sort used for fresco. it started to deteriorate already during his lifetime.
I was watching a piece on Da Vinci the other morning on A&E and they mentioned the paint experimentation but also mentioned moisture in the walls that had moved up through the foundation as another explanation for its’ deterioration.