Legends generally are not history, but the stories behind them often are. And although the legend of Saul Wahl Katzenellenbogen sounds fanciful, there is some truth and history behind it.
The legend is that, in the 16th century, Saul Wahl Katzenellenbogen became King of Poland, for just one day. There are various accounts of how this came to be. According to the version recounted in the Jewish Encyclopedia, published in 1904, Saul’s reign came about because the Polish Prince, Nicholas the Black, wanted to atone for the many atrocities he had committed while a young man. He went on a pilgrimage to Rome, where the Pope advised him that if he wanted forgiveness, he should leave his home and live the life of a wandering beggar for the next few years.
The Prince did as he was advised and wandered Europe, begging. Eventually, when the period of his punishment was up, he found himself in the Venetian city of Padua, destitute and penniless. He appealed for help, telling people that he was a prince who now needed to go home, but nobody believed him. Eventually he turned to Rabbi Samuel Judah Katzenellenbogen, the leading rabbi in the city. The rabbi was good to the prince and helped him to raise the money so that he could return home.
The rabbi had a son, Saul, who years earlier had left Padua to study in the yeshivot, or Talmudic colleges, of Poland. He had not been heard of since. When Prince Nicholas asked the elderly rabbi how he could repay him for his kindness, he gave him a picture of his son Saul. He asked the prince to try to find him.