“The sky started to change slowly,” writes Sari Soininen in her photobook Transcendent Country of the Mind. “I could see and sense his rage from the movement of the clouds, which started to get darker and darker. It felt like I had stepped into the Book of Revelation.” The Finnish photographer had in fact fallen headlong into the hallucinatory intensity of an LSD trip and was undergoing the first of several acid-induced experiences that would culminate in a prolonged bout of psychosis. What had started out as a “heavenly experience”, when Soininen first tried the drug aged 24, soon turned much darker and stranger as she became convinced that God…