Walt Whitman's Leaves of Grass exhibits elements of Romanticism in the expression of self, the mystical unity of all human experience, and in the equality regarding the individual and the world. Whitman as poet is a "seer" and an individual who is
...complete in himself...the others are as good as he, only he sees it, and they do not. [Walt Whitman Handbook]
In Section 48 Whitman declares,
I hear and behold God in every object, yet understand God not in the least,
I have said that the soul is not more than the body,
And I have said that the body is not more than the soul....
And nothing, not God, is greater to one than one's soul is....
Certainly, Whitman has a mystical interpretation of the Self. Moreover, he defines larger questions of life, such as religion, faith, God, and death mystically. In Section 5, for instance, the poet has a mystical experience between "Me" and "the Soul":
And I know that the Spirit of God is the eldest brother of my own,
And that all men ever born are also my brothers....
and the women my sisters and lovers.
And that a kelson of the creation is love.
In Song of Myself there is an expression of universality: Whitman's thoughts are the thoughts of other men, and they are thoughts that transcend time. The poet sees God in the faces of others, and he has faith in himself. This perspective is not unlike that of the Transcendentalists, who were influenced by Romanticism. They respected the individual spirit and the natural world. Also, they believed that divinity was present everywhere, in nature, and in each person. Certainly, Walt Whitman's Song of Myself reflects elements of Romanticism such as emotion, love of nature, and praise and respect for individuality.
Additional Source: Allen, Gay Wilson Allen, Walt Whitman Handbook: Hendricks House, Inc. New York, 1962.