My favorites were old time trap door cotton long johns. Not the best for warmth, but very comfortable and no bunching at the waist like two-piece long johns, where you end up with extra layers where they meet at the belt line.
For warmth, I have found the best is a thin polypropylene against the skin with a bulkier wool or cotton over that. The poly allows moisture to pass away from the skin, to be absorbed in the next layer. Wool is the best second layer, because it will pass moisture on out without losing bulk. The outer shell should be water resistant and somewhat loose. Personally, I normally just use jeans treated with Scotch Guard. You have to be talking pretty cold to make good use of this get-up, though.
The same is true for your feet. A thin poly or nylon sock, with a wool boot sock over that, and outer foot wear that is not too tight.
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