not a glimmer

not a glimmer (of an idea)

 and not a clue
Fig. no idea. A: Where's the subway? B: Sorry. Not a glimmer of an idea. How long till we're there? Not a clue.
See also: glimmer, not
References in classic literature ?
You see, there is not a glimmer of light in any of the windows, and everything is working splendidly.
Not a glimmer of light had broken in on us, so far.