The earliestform of conveyance or transfer of res mancipi at rome, which was confined to roman citizen. The process of conveyance was follows:-
1. Before five citizen above the age of puberty and a libripens(another citizen to hold a balance).
2. The alienee holding a piece of bronze.
3. Touched either the object or a representative part of it and said “I declare that this slave or thing is mine ex jure quiritium, and left it be bought for me with this piece of bronze and balance of bronze”
4. After the declaration the stroke the balance with the piece of bronze, and give it, as if it was the price to be paid to the mancipator or seller.
This formal transaction was called per aes et libram. mancipatio was not only applicable to the ceremonies of adoption, emancipation, marriage and testament. Mancipatio disappeared under law of Justinian.