Here is a potential one-off lesson. Leonardo was famous for his art work, and one technique he is the first know artist to be known to use is one point perspective. This is to help create depth, and shows the comparatible sizes of objects near and far. This is used in the Last Supper, and there are many working drawings that also show how he used this technique.

The last supper with perspective lines.

A working drawing of Leonardo Da Vinci showing perspective lines.