“Zazen Wasan” (“Song of Meditation”) was written in the early eighteenth century ce (ca. 1718) by the Japanese Zen master Hakuin Ekaku, the first Buddhist master in history to put forth the idea of common Zen, the Zen practiced by the ordinary masses, to make the complicated and mysterious Zen thinking and practice understandable in plain, everyday terms. Zazen is a term of Zen Buddhism that...