Edgar Allen Poe's obsession with "death" as the boundary moment is particularly presented at the end of his only novel, The Narrative of Arthur Gordon Pym. To describe this moment aesthetically within the discourse of sublime requires us to study whether the mind of Pym is capable of transcendence, which is also to investigate how Pym's state of mind develops during the journey, what, in his view, lies beyond the boundary condition, and how the mind forms a dramatic relation with the unattainable beyond. In the imaginary journey, we observe how a mind voyages towards all-embracing illusion, with the rational world dissolving into a "self-as-imagination" world, and finally how the mind sets up symbols as its perception of the reality of the world. When the sensible world is explored by Poe's imagination to an extreme, it is always "death" that awaits the knowing self as an ultimate state of being. The image at the voyage's end is of "whiteness" to a "perfect" degree, through which the mind might achieve a transcendence indeterminately beyond, while realising the dynamic potentials within the idea of "death", of a total Nothingness or an absolute reunion. However, the image also negated the mind's transcendence beyond a moment's duration in the textual world, as it is also through this symbol that Pym's imagination is driven to its limit. The "whiteness" of the ending bears within itself a dynamic between negation and revelation, both in and out of the test, and promises a sublimity achieved by such a peculiar tension.