Simmetry and Eye do rhyme.
Blake, as Milton and Shakespeare did, spoke words ending in "-y" not with a /i/ (a shorter "i" of words as "leave"), but with /əJ/, a higher version of the /eJ/ diphthong (a weirder version of the diphthong of the word "stake").
We have the same issue today (but not in Shakespeare's time) in A Midsummer Night's Dream, for example, where almost all the verses rhyme. Oberon, in act 3 scene 2 says:
Flower of this purple dye,
Hit with Cupid's archery,
Sink in apple of his eye.
When his love he doth espy,
Let her shine as gloriously
As the Venus of the sky.
When thou wakest, if she be by,
Beg of her for remedy.
Or in sonnet 1:
From fairest creatures we desire increase,
That thereby beauty's rose might never die,
But as the riper should by time decease,
His tender heir might bear his memory.
All the words rhyme there because all of them end in /əJ/. With time each would diverge into /i/ ("archery") or /aJ/ ("by").
By the way, the words "bright" and "night" are also pronounced with the /əJ/ diphthong. During Shakespeare, Milton and Blake's time they were undergoing the Great Vowel Shift, which made many rhymes lost for us today. If you want more info, read David Crystal's "The Oxford Dictionary of Shakesperean pronunciation", and watch these videos:
youtube.com/watch?v=WeW1eV7Oc5A
youtu.be/9FF5K8VlcRI
www.youtube.com/watch?v=eyc3q9vwhfQ
youtube.com/watch?v=5lOFAzt8fMg
THUS, whenever you hear that Shakespeare spoke General American, they're wrong, since Early Modern English pronunciation was like both and neither. (Though EME was rhotic (they pronounced the "r" when written.))