Some of old Latin poetry was written in Saturnian metre. I am under the impression that use and proper understanding of this poetic form were lost by the classical era, and we do not have a full understanding of how it works. This is in sharp contrast with many other metres — like hexameter — whose current understanding is rather complete. Wikipedia gives two different ways to parse the metre — quantitative and accentual. Many of the details are disputed. But is there anything we know for sure or essentially all scholars agree on? I assume there is not much in this category, but I do hope there is something.
This is related to the question about comparing original Latin and Greek metres, but less ambiguous.