On a moderately serious note, I've used merino wool undies and they kept my bits warmish in temperatures below minus 50. They were very comfortable even though I kept the same ones on for a month. 
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"I feel unusual.." Withnail and I
"A lot of people attack the sea. I make love to it." Jaques Yves Cousteau
"The sea once it casts its spell, holds one in its net of wonder forever." Jaques Yves Cousteau |