From the Rule of St Albert

[10] Each one of you is to stay in his own cell or nearby, pondering the Lord’s law day and night and keeping watch at his prayers unless attending to some other duty.

[11] Those who know how to say the canonical hours with those in orders should do so, in the way those holy forefathers of ours laid down, and according to the Church’s approved custom. Those who do not know the hours must say twenty-five ‘Our Fathers’ for the night office, except on Sundays and solemnities when that number is to be doubled so that the ‘Our Father’ is said fifty times; the same prayer must be said seven times in the morning in place of Lauds, and seven times too for each of the other hours, except for Vespers when it must be said fifteen times.