Ralph Waldo Emerson's quote is actually "The sky is the daily bread of the eyes." The phrase "daily bread" is a reference to the Lord's prayer, in which Christians say, "Give us this day our daily bread." The bread in the Lord's prayer refers to both literal food and spiritual food, so it is likely Emerson meant something similar when talking about the sky.

As a leader of American Transcendentalism, Emerson held nature in deep reverance, so his application of a well-known Christian phrase to his appreciation of the sky makes perfect sense. To Emerson, the sky, either during the day with the mutable beauty of the sun and clouds, or at night with the expanse of stars and the Milky Way, is a reliable provider of spiritual food. The sky is always observable, but so far away as to inspire awe and profound respect thanks to its inaccessibility. This quote encourages people to meditate on the depth and the unknowability of the sky, which is often overlooked and perhaps even disregarded thanks to its permanence.