“The construction of a machine capable of building itself might be judged to be impossible and to belong to the category of perpetual motion engines. Together with Roger Penrose, I have approached the problem in a radical manner, without the encumbrance of prefabricated units such as wheels and photoelectric cells. Our idea was to design and, if possible, to construct simple units or bricks with such properties that a self-reproducing machine could be built out of them. —L. S. Penrose”

Scientific American, June 1959

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