Heike Kamerlingh Onnes (21 September 1853 – 21 February 1926) was a Dutch physicist and Nobel laureate . He obtained his master’s degree in 1878 and a doctorate in 1879 at the University of Groningen. In 1882 he became professor of experimental physics at the University of Leiden. In 1913 he received the Nobel Prize in Physics “for his investigations on the properties of matter at low temperatures which led, inter alia, to the production of liquid helium.”
On 8 April 1911 Kamerlingh Onnes and Holst made precise measurements of the resistances of mercury and gold at 4.3 K and, cooling down further by reducing the vapor pressure of the helium, discovered that the resistance of the mercury had become “practically zero” at about 3 K. Experiments on mercury continued throughout the summer, culminating in the famous result of 26 October 1911, shown in the figure below, demonstrating that solid mercury becomes superconducting at 4.2 K. A detailed account of these events was presented by Dirk van Delft and Peter Kes in Ref. . Kamerlingh Onnes presented these results at the first Solvay meeting from 30 October – 3 November 1911. A written account was published in the proceedings of this meeting (in French) : “…la résistance à 3o absolus est plus petite que le 1/1’000’000 de sa valeur à 0o C. D’après de nouvelles recherches, cette limite peut être encore abaissée. Pour un abaissement de la température jusqu’à 2o absolus la résistance reste inférieure à cette limite.”
Translated in English [3c] : “…the resistance at 3o absolute is smaller than 1/1,000,000 of its value at 0o C. New research suggests that this limit can be lowered further. For a lowering of the temperature down to 2o absolute the resistance remains below this limit.”
 Freezing physics. Heike Kamerlingh Onnes and the quest for cold, Dirk van Delft, Koninklijke Nederlandse Academie van Wetenschappen, Amsterdam (2007), hyperlink
 D. van Delft and P. Kes, Physics Today 63, 38 (2010), hyperlink
 H. Kamerlingh Onnes, “Sur les résistances électriques”, Communications from the Laboratory of Physics at the University of Leiden, Suppl. 29 (Nov. 1911); ibid., Proceedings of “La théorie du rayonnement et les quanta. Rapports et discussions”, first Solvay Meeting, Bruxelles, 30 October – 3 November 1911, Edited by Paul Langevin and Maurice de Broglie, (a) link to the original manuscript; (b) link to a transcript; (c) link to a translation in English.