18 The principles of the spiritual life which are treated in the above-mentioned two books were also turned to the profit of souls by his daily ministry, the spiritual direction which he gave, and by the admirable Letters which he wrote. He applied the selfsame spiritual principles to the direction of the Sisters of the Visitation, which institution founded by him has preserved most faithfully, even to our own times, his spirit. The atmosphere of this particular religious community is one of moderation and loving kindness in all things. It was organized to receive young women, widows, and married women who, because of their weakness, illness, or advanced age, are physically unequal to the tasks which their religious fervor would gladly impose on them. For this reason they are not obligated to long vigils or to the changing of the holy office, neither are they required to undergo strict penances and mortifications. They are only held to the observance of their rule which is so mild and easy that all the Sisters, even those in poor health, are able to follow it.
Source: Rerum Omnium Perturbationem (Vatican.va)