You know that you had gone to the church at dawn to hear Mass, and that before that the devil had been tormenting you. You went to stand at the altar of the crucifix, though the priest had come out to Mary's altar. You stood there considering your sinfulness, fearing that you might have offended me while the devil had been troubling you. And you were considering also how great was my charity that I should have made you worthy to hear Mass at all, since you considered yourself unworthy even to enter my temple. When the celebrant reached the consecration you looked up toward him. And at the words of consecration I revealed myself to you. You saw a ray of light coming from my breast, like the ray that comes forth from the sun's circle yet never leaves it. Within this light came a dove, and dove and light were as one and hovered over the host by the power of the words of consecration the celebrant was saying. Your bodily eyes could not endure the light, and only your spiritual vision remained, but there you saw and tasted the depths of the Trinity, wholly God, wholly human, hidden and veiled under that whiteness. Neither the light nor the presence of the Word, whom in spirit you saw in this whiteness, took away the whiteness of the bread. Nor did the one stand in the way of the other. I did not block your sight either of me, God and human, in that bread, or of the bread itself. Neither the whiteness nor the feel nor the taste was taken away from the bread.

The Dialogue
St. Catherine of Siena