Horacio Carochi's Arte de la lengua mexicana (Mexico, 1645)

The Nahuatl grammar printed at Mexico City by Juan Ruyz in 1645, whose author added to it "vna cosa singular" — a four-accent notation that writes vowel length and the glottal stop the Nahua called saltillo, the two contrasts every earlier grammar had left off the page. It is also the book that records a difference between how Nahua men and Nahua women pronounced one consonant, and that tells the learner the decisive sound cannot be conveyed in writing at all.