The first known experiment to measure the
exact pressure of blood was performed by Stephen Hales on December
1, 1733. He took a live horse, attached a tube to her left crural
artery, then allowed her blood to rush through the tube and it rose
to a height of 8’3”.
He noted that “when it was at its full height, it would rise and
fall at and after each pulse 2, 3,or 4 inches”. The horse bled out,
but he performed the experiment on a horse that was about to be put
down.