The amount and character of errors due to the effect of cold upon the instrument might perhaps be a subject for discussion, and for distinct differences of opinion.
My personal experience has been that my most serious trouble was with the eyes.
To eyes which have been subjected to brilliant and unremitting daylight for days and weeks, and to the strain of continually setting a course with the compass, and traveling towards a fixed point in such light, the taking of a series of observations is usually a nightmare; and the strain of focusing, of getting precise contact of the sun's images, and of reading the vernier, all in the blinding light of which only those who have taken observations in bright sunlight on an unbroken snow expanse in the arctic regions can form any conception, usually leaves the eyes bloodshot and smarting for hours afterwards.
The continued series of observations in the vicinity of the Pole, noted above, left me with eyes that were, for two or three days, useless for anything requiring careful vision, and had it been necessary for me to set a course during the first two or three days of our return I should have found it extremely trying.
Snow goggles, as worn by us continually during the march, while helping, do not entirely relieve the eyes from strain, and during a series of observations the eyes become extremely tired and at times uncertain.
Various authorities will give different estimates of the probable error in observations taken at the Pole.

I am personally inclined to think that an allowance of five miles is an equitable one.
No one, except those entirely ignorant of such matters, has imagined for a moment that I was able to determine with my instruments the precise position of the Pole, but after having determined its position approximately, then setting an arbitrary allowance of about ten miles for possible errors of the instruments and myself as observer, and then crossing and recrossing that ten mile area in various directions, no one except the most ignorant will have any doubt but what, at some time, I had passed close to the precise point, and had, perhaps, actually passed over it..