Thayer, William Roscoe The Life and Letters of John Hay v. 1, Boston: Houghton Mifflin, 1916, p. 47. The quote comes from Rev. J. H. Gilmore:
On one occasion, at least, his enthusiasm for literature was carried to excess. “The Hasheesh Eater” had recently appeared (1857) and Johnny must needs experiment with hasheesh a little, and see if it was such a marvelous stimulant to the imagination as Fitzhugh Ludlow affirmed. “The night when Johnny Hay took hasheesh” marked an epoch for the dwellers in Hope College. It’s fifty-six years ago; but I remember it well.