Most Ragtime pieces have 4 or 2 beats in a bar, and some are even called "Two Steps". Scott Joplin and other ragtime composers experimented with adapting ragtime principles to 3 beats in a bar, which anticipated the concept of the "Jazz Waltz". Bethena (subtitled A Concert Waltz) is a perfect example of this concept, and one of the best-known Ragtime Waltzes. It was published in 1905 a year after Joplin's second wife Freddie had died from pneumonia only 10 weeks after their wedding, and we feel that his subsequent depression comes across in the music. Bethena featured on the soundtrack to The Curious Case of Benjamin Button to herald the end-titles, and capture the final mood of the film.
Here is a video of Bethena. Scroll down to see the Sheet Music, or use the links on the left-hand menu to download the sheet music, midi or mp3 files.