Helen, thy beauty is to me
Like those Nicean barks of yore
That gently, o'er a perfum'd sea,
The weary, way-worn wanderer bore
An allusion to  Helen of Troy  who in mythology is said to have been one of the most beautiful woman who ever lived. So beautiful, in fact, that according to many Greek writer–such as Homer, Herodotus, and Virgil–is believed to have been the cause the Trojan War. 
 
 While it is likely this poem was in response to Sarah Helen Whitman, who previously had written a poem to Poe entitled “To Edgar Allan Poe”, it is equally possible Poe was writing about Jane Stanard, the mother of one of Poe’s childhood friends, who died of brain cancer.  Before dying, she became deranged, which Poe observed first hand at the age of 14. Mrs. Stanard was only one of the many tragic deaths Poe encountered in his younger years, of which likely shaped his character as a poet later in life.
To Helen