What are the oldest illustrations of "Venn" diagrams? Graphical representations of intersection of sets as logical combinations are much older than Venn.
Euler and Leibniz are often quoted and the current Wikipedia article also quotes Ramon Llull but I do not really find the illustrations provided in the Wiki Commons for Llull very compelling.
I expect that these kind of ideas can be found in many other places and even older times, perhaps in disguise.
In this context I find the heraldic uses of theological diagrams such as shown here quite fascinating as a kind of medieval fashion statement.
Do you know of older examples of graphical representation of logical and/or set relations, for instance of Chinese, Arabic and Greek origin ?
(ps: at least one of the tags is a joke)
 A: You may already be familiar with Ruskey and Weston's "A Survey of Venn Diagrams," which includes a discussion of Borromean rings. Such rings are similar to the valknut and the triskelion, of which the gankyil is a type. All of these figures are quite old.
Of course these observations don't answer your question about the use of graphical representations of logical and/or set relations in antiquity. 
Plato refers to diagrams, for example, in his discussion of the double-divided line in Book 6 of Republic and in Meno when Socrates questions Meno's slave about a problem in geometry -- how to find a square double in area to any given square. I imagine more examples can be found.
An interesting project would be to find examples of "visual" language in the works of Plato, Aristotle, and Euclid.
While writing this post I came across the following two references:
Edwards, Anthony W. F. Cogwheels of the Mind: The Story of Venn Diagrams. Baltimore, Maryland: The John Hopkins University Press, (2004). 
Kuehni, Rolf. "On the Source of d’Aguilon’s Arc Color Mixture Diagram." Unpublished manuscript, 2003.
