BLAKE & WHITMAN

The congruence in the thought of William Blake and Walt Whitman noted in Swinburne's publication of 1868 draws attention in current studies.
   
From William Blake: A Critical Essay, 1868, by Algernon Charles Swinburne:

"Their casual audacities of expression or speculation are in effect wellnigh identical. Their outlooks and theories are evidently the same on all points of intellectual and social life. The divine devotion and selfless love which make men martyrs and prophets are alike visible and palpable in each. It is no secret now, but a matter of public knowledge, that both these men, being poor in the sight and the sense of the world, have given what they had of time or of money, of labour or of love, to comfort and support all the suffering and sick, all the afflicted and misused, whom they had the chance or the right to succour and to serve. The noble and gentle labours of the one are known to those who live in his time; the similar deeds of the other deserve and demand a late recognition. No man so poor and so obscure as Blake appeared in the eyes of his generation ever did more good works in a more noble and simple spirit. It seems that in each of these men at their birth pity and passion, and relief and redress of wrong, became incarnate and innate. That may well be said of the one which was said of the other: that “he looks like a man.” And in externals and details the work of these two constantly and inevitably coheres and coincides. A sound as of a sweeping wind; a prospect as over dawning continents at the fiery instant of a sudden sunrise; a splendour now of stars and now of storms; an expanse and exultation of wing across strange spaces of air and above shoreless stretches of sea; a resolute and reflective love of liberty in all times and in all things where it should be;...these are qualities common to the work of either."
 
Sarah Ferguson-Wagstaffe of Harvard University published an article titled: "Points of Contact": Blake and Whitman in the University of Maryland's Romantic Circles. The author demonstrates the connection Whitman had with Blake and comments on the similarities between the style and content of their poetry. A specific reference by Whitman to an influence by William Blake is not found. 
 
Here is  a passage showing how the fluidity of experience in the non-material world is portrayed by both Blake and Whitman:  
"16 - While the mythic characters in Blake’s poems contract and expand through perception, Whitman, or a version of Whitman, in Song of Myself, contracts and expands through touch. Whitman’s lexicon of expansion is extensive: for example, in Song of Myself, he "chant[s] a new chant of dilation" (428), he is "Partaker of influx and efflux," (462), and flies as "the fluid and swallowing soul" (799). It is also important to note that Whitman, as the subject of Song of Myself, is multiple: he incorporates "other" voices through and as his own. Ronald Beck explains that "At times the speaker seems to be a persona named Walt Whitman, at other times the voice of all mankind, at other times the voice of the mystical unity at the center of all being. Not only does the point of view shift, but it is often difficult to tell exactly when it shifts, and it is sometimes impossible to tell which voice is speaking" (35). The speaker in Song of Myself expands into a kosmos: "Walt Whitman, an American, one of the roughs, a kosmos, / Disorderly fleshy and sensual" (499-500). "Many long dumb" and "forbidden voices" filter out through his expansive body, and then, in a moment reminiscent of Blake’s "Human Form Divine" and his assertion that "every Minute Particular is Holy: / Embraces are Cominglings: From the Head even to the Feet," Whitman proclaims, "Divine I am inside and out, and I make holy whatever I touch or am touched from" (Jerusalem 69.42-3, Song of Myself 526)"

The Everlasting Gospel, (E 522)
"Love too long from Me has fled.
Twas dark deceit to Earn my bread      
Twas Covet or twas Custom or
Some trifle not worth caring for 
That they may call a shame & Sin 
Loves Temple that God dwelleth in
And hide in secret hidden Shrine      
The Naked Human form divine
.And render that a Lawless thing
On which the Soul Expands its wing"    

Jerusalem, Plate 69, (E 223)"Hence the Infernal Veil grows in the disobedient Female:
Which Jesus rends & the whole Druid Law removes away
From the Inner Sanctuary: a False Holiness hid within the Center,
For the Sanctuary of Eden. is in the Camp: in the Outline,
In the Circumference: & every Minute Particular is Holy:
Embraces are Cominglings: from the Head even to the Feet;
And not a pompous High Priest entering by a Secret Place.

Jerusalem pined in her inmost soul over Wandering Reuben         
As she slept in Beulahs Night hid by the Daughters of Beulah"

The Library of Congress collection is a source for extensive material concerning Walt Whitman as well as a repository for an impressive collection of William Blake's Illuminated Books. Their Exhibition, Revising Himself: Walt Whitman and Leaves of Grass includes a letter from Whitman in which Blake is discussed:

This letter's envelope bears the address, "William D. O'Connor, | Light House Bureau, | Treasury Department, | Washington, | D.C." It is postmarked: "New York | Sep | 28."
...

"Swinton has lately been posting himself about William Blake, his poems—has the new London edition of W. B. in two vols.8 He, Swinton, gives me rather new information in one respect—says that the formal resemblance between several pieces of Blake, & my pieces, is so marked that he, S, has, with persons that partially know me, passed them off temporarily for mine, & read them aloud as such. He asked me pointedly whether I had not met with Blake's productions in my youth, &c—said that Swinburne's idea of resemblance &c was not so wild, after all. Quite funny, isn't it?9"

The sketch of Whitman's burial vault which he designed in the form of Blake's illustration to Robert Blair's The Grave is included in this exhibition:

Wikimedia
Illustration for Blair's The Grave
Death's Door

Sites familiar to Whitman and his burial vault are visited in this video.
 
In his final writings to be included in Leaves of Grass, written in 1891 and titled Good-Bye My Fancy, Whitman wrote these lines which express Blake's sentiments as well:

"In its highest aspect, and striking its grandest average, essential Poetry expresses and goes along with essential Religion--has been and is more the adjunct and more serviceable to that true religion (for of course there is a false one, and plenty of it,) than all the priests and creeds and churches that now exist or have ever existed-"
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