According to this site it's an urban legend

A clue to the origin of the myth may be found in Patent Office Commissioner Henry Ellsworth's 1843 report to Congress. In it he states, "The advancement of the arts, from year to year, taxes our credulity and seems to presage the arrival of that period when human improvement must end." But Commissioner Ellsworth was simply using a bit of rhetorical flourish to emphasize the growing number of patents as presented in the rest of the report. He even outlined specific areas in which he expected patent activity to increase in the future.
Yes, thanks. That clears it up for me.