Louis appeared singular among seminarians, dedicating extensive time to prayer,
penance, and solitude. Uncertain of his genuineness, spiritual guides tested him.
Louis selected Fr. Leschassier, Superior of the Great Seminary, as his spiritual
director who restricted his prayer and penance practices, but Louis remained obedient.
To distract Louis from excessive recollectedness, superiors appointed him Seminary
Librarian. He utilized this position reading extensively, particularly books on Mary,
Scripture, and spirituality. He was additionally appointed Master of Ceremonies and
taught catechism to children using simple stories, becoming an expert catechist.
Desiring to preach especially to the poor, he prepared sermon notes and composed
numerous hymns.
During summer 1699, Louis and another seminarian made pilgrimage to Our Lady of
Chartres. On 5th June 1700, he was ordained priest, celebrating his first mass at
the altar of Our Lady in St. Sulpice church.