The memory palace technique began in the 5th century B.C., when Simonides of Ceos, poet, was attending an unfortunate banquet in Thessalia. While he was away to talk with a courier who asked for him outside, the hall’s ceiling crumbled, killing everyone. There was no way to recognise the corpses… Until Simonides realised that it was no problem to recall who was where, without having done any effort.
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The memory palace technique began in the 5th century B.C., when Simonides of Ceos, poet, was attending an unfortunate banquet in Thessalia. While he was away to talk with a courier who asked for him outside, the hall’s ceiling crumbled, killing everyone. There was no way to recognise the corpses… Until Simonides realised that it was no problem to recall who was where, without having done any effort.

Source: mostlymaths.net