Cause of death: heart attack
Auguste Antoine Piccard (28 January 1884 – 24 March 1962) was a Swiss physicist, inventor and explorer known for his record-breaking hydrogen balloon flights, with which he studied the Earth's upper atmosphere and became the first person to enter the Stratosphere. Piccard was also known for his invention of the first bathyscaphe, FNRS-2, with which he made a number of unmanned dives in 1948 to explore the ocean's depths.
Piccard's twin brother Jean Felix Piccard is also a notable figure in the annals of science and exploration, as are a number of their relatives, including Jacques Piccard, Bertrand Piccard, Jeannette Piccard and Don Piccard.
Source : Wikipedia