"Amazingly, Drebbel’s thermostat-equipped furnace functioned according to modern feedback control concepts, in which a sensor detects changes in the output of a system and then modifies the input to correct for those changes and bring the system back to its original state. Did Drebbel know he had created a feedback loop? “He sort of did, but he didn’t articulate it,” says Hall. “Call it embedded knowledge.” Drebbel never publicly described the mechanical underpinnings of his circulating oven, possibly to protect his product. Back then, nothing like real patent or copyright law held sway and plagiarism was rampant. Secrecy was standard alchemical practice in any case, as all the important transmutation formulae were encoded in arcane symbols." - Todd Hoff