Various, Notes and Queries, Vol. IV, Number 94…
“ Had we no other presumption to lead us to Shakspeare's true meaning but what is afforded by the expression, "into air—thin air," it ought, in my opinion, to be amply sufficient; for no rational person can entertain a doubt that Shakspeare intended the repetition, "thin air," to have reference to the simile that was to follow. The globe itself shall dissolve, and, like this vision, leave not a rack behind! In what was the resemblance to the vision to consist, if not in melting, like it, into thin air? into air unobscured by vapour, rarified from the slightest admixture of rack or cloud. ”
