The ballad of Sir Patrick Spens is based loosely on events of the thirteenth century, but is not intended as an accurate historical account but instead a literary creation that points to universal aspects of human nature.
In this ballad, the King requests that Patrick Spens, known as the greatest and most skilled of mariners, sail to Norway outside the normal sailing season. Patrick, as an expert sailor, understands the risks of such sailing. Given the technology of the period, sailors understood that they risked death in storms by sailing in winter.
When Sir Patrick Spens reads the kings's letter he realizes that to sail at this time will probably result in a shipwreck and his own death, but nonetheless out of loyalty and obedience to his king, he agrees to set sail, despite signs of impending bad weather.