In the olden days, if you were traveling outside your banking circle so to speak, you took with you credit notes that were honored in various other cities.
Sometimes these notes were coded, sometimes they were carried by external couriers in advance and sometimes you carried it yourself.
That is the whole premise of how correspondent banking established itself, which takes its roots in merchant banking.
If you were living in Paris and wanted to go to Milan for the summer, your credit note went with you (or in advance). When you arrived in Milan, the banker would let you know exactly how much you have and how you may draw down upon it.
All this was done for a fees of course. Maybe 97 cents to a Dollar or 97 pence to a Pound. Nothing was for free back then. Come to think of it, nothing is free now either.
Bankers were (and still are), very ruthless when it came to credit lines. Overstayed your vacation and no more money, unless you can get someone to back you up, no more money was provided for.
Another method was to transport a small quantity of precious metal such as gold and silver, which was kept in escrow until a credit line was established and settlement could be done.