In Canto Four of his poem John Shade (the poet in VN’s novel Pale Fire, 1962) says that the title of his first book (free verse) was Dim Gulf:
Dim Gulf was my first book (free verse); Night Rote
Came next; then Hebe's Cup, my final float
In that damp carnival, for now I term
Everything "Poems," and no longer squirm.