Much of the pioneering work in systems theory was done in the 1930-40's by different (but related) groups of academics in the fields of Systems Theory, Cybernetics, as well as Operational Research. Bertalanffy and Wienberg are progenitors of those fields, but I would stick to people like Ashby, who are much better writers. The work they produced is profound and laid the foundation for much of our modern academic disciplines and industrial practices.
There are a lot of fascinating people and fascinating work that came out of those academic groups during that period. They are too many to list, but I would give William Grey Walter and his robotic tortoise's as an example: https://www.youtube.com/watch?v=lLULRlmXkKo
This might be beyond the scope of what you want, but I would also heartily recommend Carver Mead's Analog VSLI and Neural Systems: https://www.amazon.com/Analog-VLSI-Neural-Systems-Carver/dp/...
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