During the thirteenth century there were four distinct 'psalters' in use at the same time: the 150 Our Fathers, the 150 Angelic Salutations, the 150 praises of Jesus, and the 150 praises of Mary. In an age when unity was held in such high regard, perhaps it was inevitable that these four prayer forms should eventually be combined.
The first step toward the combination of these four kinds of psalters came in about 1365 A.D. when Henry of Kalkar, the Visitator of the Carthusian Order, grouped the 150 Angelic Salutations indo decades and put an Our Father before each decade. This combined the Our Father and the Hail Mary for the first time.
Next, in about 1409, another Carthusian, Dominic the Prussian, wrote a book which attached a Psalter of fifty thoughts about the lives of Jesus and Mary to a Rosary of 50 Hail Marys. This was the first time that a special thought was ever provided for each Hail Mary bead. Eventually the 50 Hail Mary thoughts of Dominic the Prussian were divided, as Henry of Kalkar had done, into groups of ten with an Our Father in between. Many variations of this form were composed between about 1425 and 1470, but the changes were gradual, not sudden.
