1Russell, George William (Æ). Imaginations and Reveries. Dublin: Maunsel & Roberts, 1921. 136-37.
The text may be read in its entirety here. Æ was the nom de plume of the Irish writer, poet, and painter George William Russell (1867 – 1935). A mystic who also considered himself a clairvoyant, Russell was part of a group of Dublin Theosophists that included William Butler Yeats.
Russell uses some of the same phrases at the end of his poem, "Content:"
Come away, O, come away;
We will quench the heart's desire
Past the gateways of the day
In the rapture of the fire.

(Russell, George. (A.E.). Collected Poems of A.E. London: Macmillan and Co. Ltd., 1927. 297.)
Later in his life Russell gave a further explanation of how he came to imagine the dialogue inside Newgrange:
"To one who lay on the mound which is called the Brugh on the Boyne a form like that the bards speak of Angus appeared, and it cried: 'Can you not see me? Can you not hear me? I come from the Land of Immortal Youth.' And I, though I could not be certain of speech, found the wild words flying up to my brain interpreting my own vision of the god, and it seemed to be crying to me..."
(Russell, George. (A.E.). The Candle of Vision. London: Macmillan and Co., Ltd., 1919. 168.)