German physician Franz Mesmer published his foundational text 'Mémoire sur la découverte du magnétisme animal' in Paris. Mesmer claimed that an invisible, universal fluid connected all living things and that imbalances could be cured by inducing a trance state or 'magnetic sleep'. Although denounced by mainstream scientific commissions, 'Mesmerism' quickly swept across Europe, providing the first secularized, widely accessible framework for observing individuals speaking, writing, and acting entirely under the influence of their subconscious mind.

Mesmerism revolutionized the romantic conception of the mind, directly inspiring E.T.A. Hoffmann, Edgar Allan Poe, and later French Symbolists to experiment with altered states. It popularized the figure of the somnambulist as an ideal poetic oracle who could access hidden cosmic patterns while completely asleep.