In Nature, Emerson discusses communing with the natural world in the woods. He states, first, that most people interact with the woods on a superficial level. As for himself, however, he experiences nature on a deeper level. He finds a delight in it and a return to a youthful state. He asserts that nature is a ground of "reason and faith." When he is there, he feels safe:
There I feel that nothing can befall me in life, —no disgrace, no calamity ... which nature cannot repair. Standing on the bare ground,—my head bathed by the blithe air, and uplifted into infinite space,—all mean egotism vanishes. I become a transparent eye-ball; I am nothing; I see all; the currents of the Universal Being circulate through me; I am part or particle of God.
In other words, Emerson is saying that as he steps away from civilization, he is able to adjust himself to see the world through God's eyes: he becomes the "transparent eyeball" of God. He is no longer himself: he no longer has "egotism." He reunites with the divine source and becomes a "part" of God. He sees the world as God sees it.
With this new vision, Emerson can perceive that he is a part not only of God but of what he calls the "vegetable" world around him: the trees, the plants, all living things. It is this sense of symbiosis or union that creates the "delight" that nature brings.
In stating this, Emerson is articulating a core value of transcendentalism, which is that a divine source permeates nature and human beings and that, if we can pay attention and step away from human traditions and institutions, we can access divinity: we can become God's "transparent eyeball." As such, we can become aware of and communicate God's vision to the world.