In Canto One of his poem John Shade (the poet in VN's novel Pale Fire, 1962) says that a thousand years ago five minutes were equal to forty ounces of fine sand:
And there's the wall of sound: the nightly wall
Raised by a trillion crickets in the fall.
Impenetrable! Halfway up the hill
I'd pause in thrall of their delirious trill.
That's Dr. Sutton's light. That's the Great Bear.
A thousand years ago five minutes were
Equal to forty ounces of fine sand.