In 1938, doctors Eric Guttmann and Walter Maclay, two psychiatrists based at the Maudsley Hospital in London, administered the hallucinogenic drug mescaline to a group of artists, asking the participants to record their experiences visually. These artists included the painter Julian Trevelyan, who was associated with the British surrealist movement at this time. Published as ‘Mescaline hallucinations in artists’, the research took place at a crucial time for psychiatry, as the discipline was beginning to edge its way into the scientific arena. Newly established, the Maudsley Hospital received Jewish émigrés from Germany to join its ranks. Sponsored by the Rockefeller Foundation, this group of psychiatrists brought with them an enthusiasm for psychoactive drugs and visual media in the scientific study of psychopathological states. In this case, Guttmann and Maclay enlisted the help of surrealist artists, who were harnessing hallucinogens for their own revolutionary aims. Looking behind the images, particularly how they were produced and their legacy today, tells a story of how these groups cooperated, and how their overlapping ecologies of knowledge and experience coincided in these remarkable inscriptions.