There is an example of the eye, little in comparison to all the members of the body and the pupil itself is small, yet it is a great vessel.
For it sees in one flash the sky, stars, sun, moon, cities, and other creatures. Likewise, these things are seen in one flash, they are formed and imagined in the small pupil of the eye. So it is with the mind toward the heart. And the heart itself is but a small vessel…
…yet there also are dragons and there are lions; there are poisonous beasts and all the treasures of evil. And there are rough and uneven roads: there are precipices.
But there is also God, also the angels, the life and the kingdom, the light and the Apostles, the treasures of grace – there are all things.
– Macarius, Spiritual Homily 43.7