A young doctor threaded a tube into his own heart to prove it could be done safely
In 1929, against his supervisor's explicit orders, 25-year-old Werner Forssmann had a colleague insert a catheter into a vein in his own arm, then walked to the X-ray room and guided it himself nearly 60cm until it reached his right atrium. The stunt proved the heart could be safely accessed without killing the patient, founding cardiac catheterization. Forssmann shared the 1956 Nobel Prize in Physiology or Medicine for it.