The folks from Suite101.com have done some research into antique/vintage knitting, and have found some very interesting patterns for some very interesting garments.
Based on a garment from the Museum of the City of London, Lois McCarthy has devised a knitting pattern for a medieval undershirt. This one is designed for a men’s size 40, and uses fingering weight yarns on size 4 needles.
Update: This pattern is no longer available at Suite 101. Disappointing, I know.