Development of the banknote began in the Tang Dynasty during the 7th century, with local issues of paper currency, although true paper money did not appear until the 11th century, during the Song Dynasty.
A contract typically does not have to be notarized. A notary public (or simply notary) provides an acknowledgment that the signature appearing on the document is that of the person whose signature it purports to be. There is a requirement that some documents be notarized, such as a real property deed.
The courts of the United States have rules over and over again that electronic contracts are sufficient to satisfy the legal writing requirement that certain contracts must have in order be enforceable (contracts that fall under the Statute of Frauds), and electronic signatures are also sufficient to qualify as a legal signature.