Ancient Measurement Terms: Length. One foot (foot-length, foot-print or foot-space). Weight. About 70 pounds of lead. (Definitions varied between 70 and 72. Weight also depended upon material.) A thirtieth of a fother. A fifth of a sack. 5 stone. (also called fotmæl, fotmel, votmel, etc.)
Found on http://www.hemyockcastle.co.uk/measure.htm
1) Obsolete unit of measurement 
• (n.) Seventy pounds of lead.
Fot'mal noun (Com.) Seventy pounds of lead. 
Ancient Measurement Terms: Length. One foot (foot-length, foot-print or foot-space).