The French physician and scholar Alfred Maury published a series of highly innovative empirical studies based on his own sleeping habits, officially coining the term 'hypnagogic' to describe the transitional state occurring between wakefulness and sleep. Maury demonstrated how external sensory stimuli (such as a drop of water or a loud sound) are instantly translated by the sleeping brain into complex, narrative dream sequences. This marked a major shift toward analyzing dreams as physiological transformations of conscious thoughts.

Maury's clinical isolation of the hypnagogic state provided a scientific rationale for the loose, associative logic that Symbolist poets like Arthur Rimbaud were attempting to induce artificially. It gave writers a clear psychological target: the liminal edge of sleep where standard linguistic syntax breaks down into raw visual imagery.