Partial transcript from The Library of Congress:
Before I leave America I must see you again–there is no one in this wide great world of America whom I love and honour so much. With warm affection, and honourable admiration, Oscar Wilde.
The Walt Whitman Archive fleshes out the story:
On 18 January 1882 Wilde visited Walt Whitman in Camden, where the poet was then living with his brother and sister-in-law. Wilde told Whitman that his mother had purchased a copy of Leaves of Grass when it was first published, that Lady Wilde had read the poems to her son, and that later, at Oxford, he and his friends carried Leaves to read on their walks. Flattered, Whitman offered Wilde, whom he later described as “a fine large handsome youngster,” some of his sister-in-law’s homemade elderberry wine, and they conversed for two hours. Asked later by a friend how he managed to get the elderberry wine down, Wilde replied: “If it had been vinegar I would have drunk it all the same, for I have an admiration for that man which I can hardly express”