Two of the Transylvanian sale triptychs contain the clause 'apochatum pro uncis duabus.' The first document dates from 142 A.D., the second from 160 A.D. What meaning is to be attributed to 'apochatum (or apochatam) pro uncis duabus', literally 'receipted for two ounces'?
The real explanation, I suggest, is that 'apochatum pro uncis duabus', 'receipted for two unciae', refers to the present 'mancipatio', not to a previous one, and that the point of the clause is to limit the 'actio auctoritatis' to four 'unciae', a negligible sum.
'Apochatum Pro Uncis Duabus'
Available at: http://digitalcommons.law.uga.edu/fac_artchop/394