From Lady Saba Holland's memoir of her father the Rev. Sydney Smith, published circa 1855:
The reigning bore at this time in Edinburgh was ——; his favourite subject, the North Pole. It mattered not how far south you began, you found yourself transported to the north pole before you could take breath; no one escaped him. My father declared he should invent a slip button. Jeffrey fled from him as from the plague, when possible; but one day his arch-tormentor met him in a narrow lane, and began instantly on the north pole. Jeffrey, in despair and out of all patience, darted past him, exclaiming, "D— the north pole!" My father met him shortly after, boiling with indignation at Jeffrey's contempt of the north pole. "Oh, my dear fellow," said my father, "never mind; no one minds what Jeffrey says, you know; he is a privileged person; he respects nothing, absolutely nothing. Why, you will scarcely believe it, but it is not more than a week ago that I heard him speak disrespectfully of the equator!"
I think it's fairly clear that the meaning of the bolded sentence is "My father said that my father fantasized about inventing a physical device for slipping away from that boring person."
However, what exactly is a "slip button," or what would the circa-1855 reader have understood the circa-1797 Rev. Smith to have meant by the phrase?
Google tells me that a "slip button" may be some part of a drill assembly, such as in an oil well, which coincidentally is also something which bores; but I'm not sure that a clergyman in the 1790s would be making oil-well jokes. I expect the answer to be something about clothing, somehow, but I can't find any textual support for that idea. Anyway, I'd still appreciate an explanation of what a "slip button" is in the borehole context, because I can't make head or tail of the few references I found!
(Most Google results for "slip button" these days are about the button that turns on all-wheel drive mode in your car when it's icy out. That's clearly unrelated to the reverend's meaning here.)