Willem Einthoven, after completing in 1901 the development of a string galvanometer far more sensitive than Ader's (whom he explicitly cites in his 1901 paper 'Un nouveau galvanomètre'), achieves on 22 March 1905 the first successful clinical recording of a human electrocardiogram at the Academic Hospital in Leiden. The instrument weighed 270 kg and required five people to operate; the patient's limbs were immersed in buckets of salt water as electrodes. It marks the beginning of electrocardiography as a clinical diagnostic tool.