The Book of Hours was the prayer book of the laity during the Middle Ages. Its core was the Little Office of Our Lady, a set of devotional texts to be recited at each of the canonical hours, which became part of the Psalter in the 11th century. During the 11th and 12th centuries the developing veneration of the Virgin Mary among the laity and a wish to bypass the sometimes immoral and ill-educated clergy, led to the need for a book of daily devotion, and the Book of Hours first appeared in the 13th century. It contained texts from the Psalter and the Breviary as well as other Hours, hymns and prayers, and was almost invariably illustrated. As the Book of Hours was made to order and was not under Church control the purchaser could specify the texts it was to contain and could also determine the programme of illustration. The result was a book of prayer designed for a particular person, to fulfil all her requirements for private devotion. One form of private prayer that became popular during the 12th century was meditation on the humanity of Christ, which was seen by religious writers as the first step towards contemplation or unity with the Divine. Many of these writers advised the meditator to first visualise the events of the Incarnation and Passion, then to imagine being there and to summon up the appropriate emotions. The illuminations in the Book of Hours facilitated the visualisation of the scenes and thus assisted the owner's meditation.