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Back to Mr Rosenblatt. He was a psychologist, fascinated by how the brain learns. So when he built his version of a neuron, he didn't write it as software. He built it as a machine you could walk up to and touch.
He called it the Perceptron, and it was the size of a room.
A camera pointed at a card with a shape on it, a letter, say, or a square. The camera broke the picture into little patches of light and dark, and turned each patch into a number. Those were the inputs.
Each input ran into a dial, a physical knob. The knob's setting was the weight: how much that patch of the picture counted. Turn a knob up, and that patch mattered more. Turn it down, and it mattered less.
The machine added up all the dialed-down signals and made a single guess: "this is the shape" or "this is not."
And here is the beautiful part. Each dial was turned by a small motor. So when the machine guessed wrong, it could reach in and turn its own knobs, all by itself.