Most of our critical thinking can be attributed to logical argument. An old and well-established logical rule is the syllogism: (1) All humans are mortal, (2) All Greeks are humans, (1) and (2) conclude via syllogism that (3) All Greeks are mortal. This form (AAA), with A indicating "All," is referred to as Barbara, a mnemonic. In the 1883 text Studies in Logic (John Hopkins University) edited by C.S Peirce, Allan Marquand designed a machine to produce syllogisms with the design illustrated in the above diagram. Marquand's paper was entitled "A Machine for Producing Syllogistic Variations." The design is interesting and appears to serve as a mechanical aid to combinatorics. The hand crank is attached to d. There are "sectors" for each of the d,e, and f wheels causing friction against a, b, and c. Variations are achieved by wheels d, e, and f having diameters of powers of 2: 1, 2, and 4 inches respectively. Mechanical counters are similar except that finger protrusions are used on identically sized wheels to create combinations.
I recall first seeing this image in a science museum - the Boston Museum of Science if I recall, in their wonderful Model Section. The image is Fritz Kahn's mechanical model of digestion. The National Institutes of Health (NIH) has a special exhibit celebrating the different views and perspectives of the body in an exhibit called Dream Anatomy. This design belongs to the history of automata, and adds some new twists in its detailed anatomical representation. Fritz Kahn, the designer, produced a variety of creative infographics for the relationship of man to machine-- "Maschine Mensch"
I had a discussion online with Ray Winstead who recently retired from the Indiana University of Pennsylvania in Biology. Ray has a page which I came across and found a diagram which is most compelling both for its biological meaning as well as the design (created by William Standaert):
The design is a flow model which receives energy in the form of sunlight and this energy undergoes a "food chain" transformation. The transformation begins with producers (e.g., plants) which are eaten by herbivores, which are in turn eaten by carnivores, to end the chain with the top carnivores (e.g., humans). There are actually 2 sub-chains in this diagram: one for consumers of live material, and the other for detritus. These types of models can be simulated: common model types used by ecologists include Odum graphs, System Dynamics, and compartmental models. Further information with a more abstract model can be found in the Wiki link on energy flow.