Annalen, Der Physik, Vierte Folge, Band 14 Heft 1 Leipzig 1904, original orange papers, first edition, first impression, Willem Einthoven's paper: Über einige Anwendungen des Saitengalvanometers [p.182 - p.192],

This is the first paper ever published by Einthoven on his development of the electrocardiogram (ECG) a machine used to record the hearts electrical activity. It was in 1924 that Einthoven was awarded the Nobel prize in medicine for his invention of the ECG. This article is his first report that was the basis for the award.