Gradus ad Parnassum (n.)
Latin, literally "A Step to Parnassus," the mountain sacred to Apollo and the Muses; from Latin gradus "a step; a step climbed; a step toward something" (from PIE root *ghredh- "to walk, go"). Also see Parnassus. It was the title of a dictionary of prosody used in English public schools for centuries as a guide to Roman poetry. The book dates from the 1680s. Also the name of a treatise on musical composition written in Latin by Johann Joseph Fux, published in Vienna in 1725, and of a much-used book of exercises for piano.