This could have been done earlier, and can also be done much better than what I am showing here. There are much better images of the two paintings of the Mona Lisa, and I am working from a print copy of an article in the American Scientist, November-December 2015, page 405. The most famous Mona Lisa is in the Louvre Museum in Paris, France, but a second Mona Lisa is in the Prado Museum in Madrid, Spain. They are nearly identical and were obviously painted at the same time in the same studio by Leonardo da Vinci. The paintings were probably done as a team effort with his assistants doing much of the paintings’ background and fill-in areas of clothing and hair, but the faces, hands and sleeves are clearly the work of an absolute master. What is startling about these two paintings is that they are slightly offset in point of view by about the distance between a person’s eyes. Thus when the two paintings are placed side by side and viewed cross-eyed you can see them as a single stereo three-dimensional (3D) image.
You may view this picture in 3D by sitting 18 inches from your 20-inch computer screen, and holding a tip of a pencil between her lips, your eyes about halfway to the screen with your eyes looking at the pencil tip. Your eyes will be crossed while looking at the tip and you will see two separate images of her face. Now move the tip slowly toward your eyes, and when it is about 3/4 of the way from the screen to your face you will see the images merge into a stereo 3D image. It will help to rock your head slowly side to side an inch or two to help your eyes to fuse, and to level the image. When the image fuses, lower the pencil out of the way, and move your face forward and back, about an inch, to enhance the 3D effect. When you are successful with that, spend time looking at the face and hands to see their even more life-like effect, and view the background near her head to see the flat backdrop painting used for scenery.
It is strange that in 1510 the most famous painting in the world, because of its superb painting skill and emotional subtlety, is also the first and perhaps the only 3D picture made until the 1840s, some 330 years later, when multiple lens photographs were made so there would be duplicates from a single very long exposure sitting. When it was discovered they could be seen as 3D, a whole industry of stereo photos became popular. Viewmaster became a way to travel the world. Even today it’s a major cinema event when Hollywood makes a 3D movie.
500 years after being created Mona Lisa comes to life in a 3D painting.