The passage in the Tempest, Act III. Scene 1., as quoted from the first folio, stands thus:
"I forget:
But these sweet thoughts do even refresh my labours
Most busie lest, when I do it."
This was altered in the second folio to
"Most busie least, when I do it."
Instead of which Theobald proposes,—
"Most busyless, when I do it."
But "busyless" is not English. All our words ending in less (forming adjectives), are derived from Anglo-Saxon nouns; as love, joy, hope, &c., and never from adjectives.
My conjecture is that Shakespeare wrote—