Kamerlingh Onnes's 1911 resistance-versus-temperature plot for mercury

APR 08 1911

The original 1911 graph in which the resistance of a mercury capillary falls vertically to zero just below 4.2 kelvin. This is the primary document of the discovery of superconductivity, drawn by Kamerlingh Onnes's own laboratory. Nothing else in the story is this directly evidential.