You should have seen it around 1815:
To send a letter from the United States to Britain, you addressed it by domestic U.S. Mail to a shipping house on the coast, enclosing money to cover ocean travel and inland postage in Europe. The captain of the transatlantic ship was the real carrier, and passengers sometimes undercut him by agreeing to take letters at 25 to 50 cents apiece. But the total cost of a letter from the New World was never less than a day’s wages, or two days’ wages in the other direction. Time taken was rarely less than two months, even if the letter was an important official dispatch carried by fast frigate. In 1817 the new president, James Monroe, wrote to John Quincy Adams in London, summoning him to be Secretary of State, on 6 March; it reached Adams only on 16 April, the fastest of four identical letters sent by different routes.