In Canto One of his poem Shade (the poet in VN’s novel Pale Fire, 1962) mentions Sherlock Holmes:
And then the gradual and dual blue
As night unites the viewer and the view,
And in the morning, diamonds of frost
Express amazement: Whose spurred feet have crossed
From left to right the blank page of the road?
Reading from left to right in winter's code:
A dot, an arrow pointing back; repeat: