1906: President Roosevelt and Mr. Hearst stand as far as the poles asunder.
1899: Two writers of Marrano origin, wide as the poles asunder in gifts of mind and character ...
1795: ... they were brothers by blood, but their hearts were as far asunder as the poles.
1784: [T]he mutual attraction of hearts does not follow the ratio of their distance, and ours would be in contact were they distant as the poles asunder.
This stock phrase seems like it ought to have a known origin — maybe from a poem? — but I have not been able to track it down in a few minutes of looking.
The oldest similar phrase I found in a Google Books search was from Josiah Eveleigh:
1719: ... a Subordination of distinct Beings, which is as wide as the Poles from a relative Subordination of the Son to the Father in the same Being ...
In latter days the phrase is often quoted as "poles apart" rather than "asunder."
UPDATE synthesized from RaceYouAnytime and JEL's answers below:
Young, 1753: Long as I live, I stand a world between you / And keep you distant as the poles asunder.
Dryden, 1690: For two such Tongues will break the Poles asunder; / And, hourly scolding, make perpetual Thunder.
So we've got a poetic usage of "break the poles asunder" from 1690, and a usage of "wide as the poles" from 1719; and then the two memes combine into "distant as the poles asunder" in another play as early as 1753.
I've also located a similar phrase in C. J. Hempel's translation of Schiller's Semele:
1861: The mighty sea shall in defiance leap / O'er barriers and the unfathomable abyss / Shall send forth peals of thunder; / Lightnings hiss / Through gloomy night, and rend the poles asunder!
My German is not good enough to know if Schiller's original wording directly suggests the phrase, or if Hempel was just looking for a rhyme and happened to remember his Dryden.
1782: Empöret steigt das Meer, Gestad' und Damm zu Hohne, / Der Blitz prahlt mit der Nacht, und Pol und Himmel krachen, / Der Donner brüllt aus tausendfachem Rachen ...
The proximity of "Pol und Himmel" does suggest that at least some writers are envisioning celestial poles rather than the poles of the Earth in this connection.