“It was odd that I should discover eternity in this way, long before I knew what eternity was, and even before I had learned the proposition that all man are mortal - yes, while I was actually living in eternity myself. It was as if a fish were suddenly to discover the water it swam in. I mentioned this to my grandfather one day when we happened to be alone in the living-room.”

"She's Dead?"
Shades of the World (1985)

Source: Song lyrics, The Kick Inside (1978)

On his inspiration, when he was still learning English and walking alone in the fields of Long Island, to take up the reading of No Cross, No Crown by William Penn, after having first set it aside upon realizing it was a religious book. In Memoirs of the Life and Gospel Labors of Stephen Grellet (1860), p. 20
Context: I was suddenly arrested by what seemed to be an awful voice proclaiming the words, "Eternity! Eternity! Eternity!" It reached my very soul — my whole man shook — it brought me like Saul to the ground. The great depravity and sinfulness of my heart were set before me, and the gulf of everlasting destruction to which I was verging. I was made to bitterly cry out, "If there is no God — doubtless there is a hell." I found myself in the midst of it.

Source: Too Loud a Solitude

The Letters Of William Blake https://archive.org/details/lettersofwilliam002199mbp (1956), p. 50
1790s

Time

"I Knew a Woman," ll. 22-28
Words for the Wind (1958)
Context: Let seed be grass, and grass turn into hay:
I'm martyr to a motion not my own;
What's freedom for? To know eternity.
I swear she cast a shadow white as stone.
But who would count eternity in days?
These old bones live to learn her wanton ways:
(I measure time by how a body sways.)

Source: My Name is Red

The Time of Dreams.