Hakuin Ekaku (白隠慧鶴) (1686-1769) was one of the most influential figures in Japanese Zen Buddhism. He possessed an unusual ability to convey the meaning of Zen to large numbers of people from all classes and religions. His work had a profound effect on Zen study & painting. Master Hakuin published many texts, including "Yasen kanna" (夜船閑話), "Idle Talk on a Night Boat" - a work on health-improving meditation techniques (PDF, PDF)
Related: The Sound of One Hand: Paintings and Calligraphy by Zen Master Hakuin