No single thing will make 
your wilderness experience 
more pleasant, warmer, cooler, 
drier than a modern "hydrophyllic" 
undershirt. The synthetic fiber in 
these shirts transports perspiration 
from your skin to the outside where it 
evaporates. You stay dry and warm. 
Consult a local outdoor store for all the 
options. The price is worth it, so make 
sure you have at least one wicking layer.