Like those Nicean barks of yore
That gently, o'er a perfum'd sea,
The weary, way-worn wanderer bore
To his own native shore.
On desperate seas long wont to roam,
Thy hyacinth hair, thy classic face
Thy Naiad airs have brought me home
To the glory that was Greece
And the grandeur that was Rome
Lo! in yon brilliant window-niche
How statue-like I see thee stand!
The agate lamp within thy hand
Ah! Psyche from the regions which
Are Holy Land!
A beautiful mythological princess who ended up marrying the god of love himself, Eros. 
 
 For the sake of Psyche’s safety, Eros told Psyche that she could never look at him when they made love. Unfortunately, eventually Psyche became curious and shined an agate lamp on Eros.  This ties back to the agate lamp from the previous line .
To Helen