Clark:
Railroads generally tried to get out of as much weighing as possible.
In the steam era there were several Freight Bureaus (Western Weighing
& Inspection Bureau, EWIB, SWIB, etc) that would establish an origin
or destination weight agreement based on the weight of a bag, pallet,
boxes etc. The shipper would put the net weight on their bill of
lading with the tare weight and the carrier would ascertain the
freight chages off the customer certified weights. Bulk commodities
such as cement, rock, coal, lumber, etc would be weighed by the
railroad over a weigh in motion scale, hump scale or static scale.
Generally the shipper wanted lumber weighed as far along the trip as
possible as lumber would actually dry enroute and become lighter. I
worked in the Mopac station department for a few years and worked with
WWIB to get weight agreement established - if you have any questions
let me know.

Charlie