There is one page (above, [1][2]) in “Letter on the Deaf and Dumb” on which Diderot illustrates the concept of medium specificity down to a T.

At the top of the page is a musical composition represented by musical notation. Below that is a drawing of a reclining woman.

Both represent a dying woman.

Diderot answers the question “why is it that what appeals to our imagination in poetry will not please our eyes when painted?“