So far he hadn't discovered a single mirror in the entire house!
Based on this, consider the use of a single, 100% reflective, disk-shaped mirror at the L1 point.
Yet whenever I looked closely at my surroundings, there was not a single mirror to be seen anywhere.
Three or four women shared a single mirror.
Each scene ends with all of the characters in the room crowded around a single mirror and gazing at their own reflections.
There was a single mirror on her desk; small, plain, and functional.
As Alice found through the looking-glass, a single mirror causes left and right hands to switch.
If they are all parallel, the effect is the same as a single mirror (slide a pair to cancel the third).
It used a single mirror to reflect the image of an astronomical object to the observer's eye.
A single mirror hung on the wall, but that was not ordinary at all.