Poem Analysis Help? Belshazzar Had A Letter

Hey guys :) I'm new to these forums, but I just want to say I'm a crazy reader, love Sylvia Plath and everything. But, also, if you guys would help me out, that'd be great! I have a presentation on this poem, and I've searched EVERYWHERE for a complete analysis on this poem, and can't find it. I have some of the chunks of it, but not all of the information.


Belshazzar had a letter -
He never had but one -
Belshazzar's Correspondent
Concluded and begun
In that immortal Copy
The Conscience of us all
Can read without its Glasses
On Revelation's Wall-


thank you very much! :D If you help me out, that'd be amazing.