Laudator Temporis Acti

Andrew Dalby, "Dining with the Caesars," in Food and the Memory: Proceedings of the Oxford Symposium on Food and Cookery 2000, ed. Harlan Walker (Totnes: Prospect Books, 2001), pp. 62-88 (at 76; footnote omitted):

[U]ntil Nero's time the only safe way to add water to wine was to add it recently boiled, still hot. The Romans knew this, although, unaware of microbes, they had no idea why it was. They liked to add ice to wine, and even carried snow to Rome and stored it there for the purpose, but they knew that it would sometimes make them ill. Nero's great idea was to boil water, to seal it in a jar, and then to embed the jar in snow. This produced ice-cold water that was more or less sterilized, to add to wine, and I think it will be agreed that it was a significant contribution to human happiness, or at least to the happiness of those in Rome who could afford large quantities of snow in summer.

I am not alone in believing this to be one of Nero’s greatest achievements. Nero himself thought as I do, to judge from the fact that his great invention was at the front of his mind on his very last day on Earth. Expecting to be captured at any moment, Nero was hiding alone in a garden not far from Rome. Lacking any other supplies, 'he scooped up water from a pool to drink from his cupped hands. "Here is Nero's very own iced water," he said' (Nero 48). Whatever Suetonius' immediate source, the story, if true, must come from the memories of the few slaves who had remained with Nero during his flight.