"But these sweet thoughts, do even refresh my labour,
Most busiest when I do it."
The sense will be perhaps more evident by a mere transposition,
preserving every word:
"But these sweet thoughts, most busiest when I do
My labour, do even refresh it."
Here we have a clear sense, devoid of all ambiguity, and confirmed by
what precedes; that his labours are made pleasures, being beguiled by
these sweet thoughts of his mistress, which are busiest when he labours,
because it excites in his mind the memory of her "weeping to see him
work." The correction has also the recommendation of being effected in
so simple a manner as by merely taking away two superfluous letters. I
trust I need say no more; secure of the approbation of those who (to use
the words of an esteemed friend on another occasion) feel "that making
an opaque spot in a great work transparent is not a labour to be
scorned, and that there is a pleasant sympathy between the critic and
bard--dead though he be--on such occasions, which is an ample reward."