I was recently reading Martin Luther's commentary on the Sermon on the Mount (English translation by Charles A. Hay, 1892) and I was intrigued by a reference to "the legend of the Knight Tondalo".
Here is what Luther wrote, when discussing the strait gate and narrow way (Matthew 7:13,14), and specifically Luther's concept of battling against the devil, the world and one's own flesh:
The ancients have admirably depicted this in the legend of the Knight Tondalo (except that they did not rightly apply it, and interpreted it of purgatory or the punishment of souls after this life,) how he had to pass over a small bridge that was scarcely as broad as a hand, with a burden on his back, and under him a sulphurous pool full of dragons, and besides there was one coming towards him to whom he had to give place.
(The full text of this book, matching my print version, is online here: https://beggarsallreformation.blogspot.com/2005/10/commentary-on-sermon-on-mount.html)
Some basic web searches for "Tondalo", "pool of dragons and sulfur" and similar terms do not turn up anything relevant. I'm thinking perhaps the form of the name Luther used is different from the modern one. It also would not be unusual if he had some of the details wrong or adapted them for his purposes in explaining the Bible.
I don't know which "ancients" he is referring to, either, although it seems most likely to me that this would be a Greek or Roman hero figure, rather than an actual "knight". Or maybe the story comes from an old Germanic legend or some other tradition, instead.
I would like to find out:
- What is the underlying myth or legend Luther is referencing?
- Where can I find a more complete version than this short reference?