John Cassian, The Institutes XI.14: How it suggests that a man may seek to take holy orders

But sometimes it creates a wish to take holy orders, and a desire for the priesthood or diaconate. And it represents that if a man has even against his will received this office, he will fulfil it with such sanctity and strictness that he will be able to set an example of saintliness even to other priests; and that he will win over many people, not only by his manner of life, but also by his teaching and preaching. It makes a man, even when alone and sitting in his cell, to go round in mind and imagination to the dwellings and monasteries of others, and to make many conversions under the inducements of imaginary exultation.