Is it ensure, insure, or assure?
devotional book widely popular in the later Middle Ages. The book of hours began to appear in the 13th century, containing prayers to be said at the canonical hours in honour of the Virgin Mary. The growing demand for smaller such books for family and individual use created a prayerbook style enormously popular among the wealthy. The demand for the books was crucial to the development of Gothic illumination. These lavishly decorated texts, of small dimensions, varied in content according to their patrons' desires.