The French sinologist Marie-Jean-Léon, Marquis d'Hervey de Saint-Denys, anonymously published 'Les Rêves et les Moyens de les Diriger' (Dreams and How to Guide Them). Based on a private journal he kept since the age of thirteen, Saint-Denys outlined the first precise methodology for achieving what is now known as lucid dreaming. He proved that a sleeper could become fully aware that they are dreaming and actively manipulate the dream scenery, proposing that memory and association are the absolute drivers of dream imagery.

This book revolutionized avant-garde thought by demonstrating that the subconscious mind could be consciously directed like a work of art. It suggested to early modernist and surrealist poets that they could act as active directors of their own nocturnal visions, transforming sleep from a passive vulnerability into a highly controlled creative laboratory.