My old Auto mechancs teacher told a story:
Had a front wheel drive car with disk brakes that just wouldn't stop. (Probably very early '80s.)
After lots of messing,
(And one trip through a red light with both feet on the brake pedal during a test drive):
He decided to plumb a gauge into the master cylinder and see what the pressure was in the front lines. (This before anti-lock brakes)
He said he could get 4,000 psi out of the master cyl in the shop with both feet pressing the pedal. And speculated that he was getting a lot more than that when it rolled through that red light.