Let me say first, "purgatory" as used here is a shorthand for the notion that there is some kind of temporary purging or post death preparation of the soul before it enters the eternal bliss of heaven. However, others associate it with the Roman Catholic Church's exact dogma where that Church holds a "super treasury of merit," etc.
I was reminded of this when discussing the issue with an Eastern Orthodox believer who is very anti-Roman Catholic and he rejected "purgatory," bitterly mocking it. But then he admitted his church/he believes in such a place of post death preparation of the soul before it enters heaven; but he would never call it "purgatory" which he associates with the Roman dogma (like them holding the keys to a "super treasury of merit") that he hates.
But from a letter from Benjamin Franklin to “Mrs. Partridge” on the death of one Ben Kent. The letter is dated November 25, 1788:
You tell me our poor friend Ben Kent is gone, I hope to the regions of the blessed; or at least to some place where souls are prepared for those regions! I found my hope on this, that though not so orthodox as you and I, he was an honest man, and had his virtues. If he had any hypocrisy, it was of that inverted kind, with which a man is not so bad as he seems to be. And with regard to future bliss, I cannot help imagining that multitudes of the zealously orthodox of different sects, who at the last day may flock together, in hopes of seeing each other damned, will be disappointed, and obliged to rest content with their own salvation. Yours, &c. B. Franklin.