I think it was me that answered your other question about this excellent poem by Emily Dickinson, where I focused on the series of metaphors that are used to compare the brain to a number of different things. Really, the poem is built around the three metaphors that I talked about in my previous answer (linked below for your convenience). The only other devices that you can see in this poem are alliteration or the repetition of consonant sounds at the beginning of words. Alliteration occurs in, for example, the very last line of the poem, which talks about how the brain and the "weight of God" are so similar in weight that they will differ--if indeed they do differ-as "Syllable from Sound." Clearly, the implication is that they are very similar, and the alliteration in the "s" sound helps round off the poem in an unforgettable fashion.
Apart from the use of alliteration and the metaphors already referred to, this poem does not use any other poetic devices. It is amazing to reflect how Dickinson created such incredible poems that really force us to re-examine our view of the world in such short length and in such simple language.