This is one of the references I've found:

I am convinced that there is a North-West passage to the intellectual world;

and that the sould of man has shorter ways of going to work on knowledge

and instruction than we generally take with it.

Sterne, Tristram Shandy, quoted in E.M.Forster's Commonplace Book. pg 3 (come

Shandy bk.5, ch.42)

Any others?

--

Alex Warwick (23.6.03) brings:

The first refernces to the northwest passage would most likely be in
French or Spanish or Italian.
I think the first explicit expedition to look for it was led by the
Florentine Verrazano, who was commisssioned by the king of
France, in 1524.
Before that, they were trying a North East passage.