Of Leo Perutz's unfinished novel 'Mayflower,' only the first two of originally four chapters survive today.
Notes on verification
Confirmed by the DNB archivist's blog post describing the actual Nachlass materials, which is the authoritative primary source (holder of the manuscript). However, the specific detail of '2 of 4 chapters' is not independently corroborated by a second separate source; other sources only confirm the novel is an unfinished fragment.