Aelred of Rievaulx, De institutione inclusarum or On the Institution of the Recluse (1109/10–1167)—Written by an English monk, this work contains a description of the devotional practices of the recluse who concentrates on images of the life and death of Christ in order to identify mystically with the event. It illuminates the practices of individuals like Christina of Markyate who turned to illustrated psalters for their devotions in the twelfth century.

Bernard of Clairvaux, Letter to William of St. Thierry (1125)—Written by the Cistercian founder of the monastery of Clairvaux who would later be canonized as St. Bernard (1091–1153), this critique of the Benedictine (especially Cluniac) approach to the visual arts in a sacred context is part of the twelfth-century debate over the appropriateness of sacred art.

Etienne Boileau, Le Livre des métiers (1268)—Written in Paris, this work discusses the...