hornbook is a Noun
 The first book for children, or that from which in former times they learned their letters and rudiments; -- so called because a sheet of horn covered the small, thin board of oak, or the slip of paper, on which the alphabet, digits, and often the Lord`s Prayer, were written or printed; a primer. "He teaches boys the hornbook." Shak.
 A book containing the rudiments of any science or branch of knowledge; a manual; a handbook.
Allow Updates from cubepost.red