title illustration of Bellarmine's catechism showing people of all ages and angels adoring the Sign of Redemption: in what might by a Blessed Sacrament host, a cross beneath which the "IHS" and the three nails.
This catechism was created in 1614 by doctor of the church, Cardinal Robert Bellarmine. It is richly illustrated with images to assist learning and memory.

Saint Gregory the Great, Apostle of the Angels, Book 9 of his letters, book 9

presents this [volume] with writings for those reading and pictures for those uneducated ones looking on: because even the ignorant see in these things that which they ought to follow: they, who do not know the letters [i.e., who are illiterate], read in those things [i.e., the pictures].

[ed. note:  a picture is worth a thousand catechetical words]