Since the characteristica universalis is diagrammatic and employs pictograms, the diagrams in Leibniz's work warrant close study - wikipedia 
On at least two occasions, Leibniz illustrated his philosophical reasoning with diagrams. One diagram, the frontispiece to his 1666 De Arte Combinatoria, represents the Aristotelian theory of how all material things are formed from combinations of the elements earth, water, air, and fire.
Diagrammatic reasoning. Diagrammatic reasoning is reasoning by means of visual representations. The study of diagrammatic reasoning is about the understanding of concepts and ideas, visualized with the use of diagrams and imagery instead of by linguistic or algebraic means. - wikimedia
These four elements make up the four corners of a diamond (see picture). Opposing pairs of these are joined by a bar labeled "contraries" (earth-air, fire-water).
File:Wikipedia_article-creation-2.svg
At the four corners of the superimposed square are the four qualities defining the elements. Each adjacent pair of these is joined by a bar labeled "possible combination"; the diagonals joining them are labeled "impossible combination".
A conceptual graph of "Elsie the cat is sitting on a mat."
Starting from the top, fire is formed from the combination of dryness and heat; air from wetness and heat; water from coldness and wetness; earth from coldness and dryness.
File:PeirceAlphaGraphs.svg
This diagram is reproduced in several texts including ''Saemtliche Schriften und Briefe'' (''Saemtliche Schriften und Briefe'', Reihe VI, Band 1: 166, Loemker 1969: 83, 366, Karl Popp and Erwin Stein 2000: 33).
File:Characteristica_universalis_diagram.jpg