Cordiform (heart-shaped) books. From top:
1. Le Chansonnier Cordiforme/Chansonnier de Jean de Montchenu (Heart-shaped Song Book).
2. Caspar Meuser: Betbüchlein ür allerlei Anliegen (Small Prayer Book for All Occasions), ca. 1580.
3. Livre d’heures à l’usage d’Amiens (Book of Hours used in Amiens), ca. 1500s.
4. The Heart Book. Danish, ca. 1550s. Via Daniel Mitsui.
Related: Master of the View of St. Gudula.