Sonnet XXI (21)

So is it not with me as with that Muse,

Stirr'd by a painted beauty to his verse;

Who heaven itself for ornament doth use, 

And every fair with his fair doth rehearse; 

Making a couplement of proud compare, 

With sun and moon, with earth and sea's rich gems,

With April's first-born flowers, and all things rare 

That heaven's air in this huge rondure hems. 

O' let me, true in love, but truly write, 

And then believe me, my love is as fair 

As any mother's child, though not so bright 

As those gold candles fix'd in heaven's air: 

   Let them say more than like of hearsay well;

   I will not praise, that purpose not to sell. 

The muse is identified with the poet in question. As to the words "painted beauty," 

Possibly some particular poet may be intended. 

Every fair with his fair, &c. Compares everything beautiful with the beauty which he celebrates. 

Couplement. Represented in Q. by "cooplement." Of proud compare. Coupling, in his exalted and inflated comparisons, the beauty which he celebrates with objects specified in the three following lines. 

A poet's rage. The product of poetical enthusiasm. 

Stretched metre. Mere inflated words. Q. has the spelling "miter." 

This huge rondure. Possibly the vast circumference of the limiting horizon, or possibly the vault of heaven. On the whole, the former sense seems the more probable. 

I will not praise, & I will not indulge in extravagant laudation, as sellers do, wishing to part with what they praise.