This stunning letter can be found in the Letters of Note book. And on the audiobook, it’s read by Alan Cumming.

Walt Whitman—the “father of free verse”—is arguably one of the most important figures in literary history and certainly one of the greatest poets, having published, in 1855, Leaves of Grass, a self-financed collection of his life’s poetry which at the time was denounced by many critics due to its unconventional and “obscene” verse, but which has since gone on to be immeasurably influential. In May of 1889, as Whitman was approaching his 70th birthday, the great Mark Twain wrote this beautiful and suitably grand letter of congratulations to Whitman—a stunning, four-page love letter to human endeavour as seen during the poet’s lifetime

Hartford, May 24/89

To Walt Whitman:

You have lived just the seventy years which are greatest in the world's history & richest in benefit & advancement to its peoples. These seventy years have done much more to widen the interval between man & the other animals than was accomplished by any five centuries which preceded them.

What great births you have witnessed! The steam press, the steamship, the steel ship, the railroad, the perfected cotton-gin, the telegraph, the phonograph, the photograph, photo-gravure, the electrotype, the gaslight, the electric light, the sewing machine, & the amazing, infinitely varied & innumerable products of coal tar, those latest & strangest marvels of a marvelous age. And you have seen even greater births than these; for you have seen the application of anesthesia to surgery-practice, whereby the ancient dominion of pain, which began with the first created life, came to an end in this earth forever; you have seen the slave set free, you have seen the monarchy banished from France, & reduced in England to a machine which makes an imposing show of diligence & attention to business, but isn't connected with the works. Yes, you have indeed seen much — but tarry yet a while, for the greatest is yet to come. Wait thirty years, & then look out over the earth! You shall see marvels upon marvels added to these whose nativity you have witnessed; & conspicuous above them you shall see their formidable Result — Man at almost his full stature at last! — & still growing, visibly growing while you look. In that day, who that hath a throne, or a gilded privilege not attainable by his neighbor, let him procure his slippers & get ready to dance, for there is going to be music. Abide, & see these things! Thirty of us who honor & love you, offer the opportunity. We have among us 600 years, good & sound, left in the bank of life. Take 30 of them — the richest birth-day gift ever offered to poet in this world — & sit down & wait. Wait till you see that great figure appear, & catch the far glint of the sun upon his banner; then you may depart satisfied, as knowing you have seen him for whom the earth was made, & that he will proclaim that human wheat is worth more than human tares, & proceed to organize human values on that basis.

Mark Twain