“Weighed in the balance and found wanting”
What it means
Assessed and judged inadequate.
Where it comes from
A balance compares an unknown weight against known standards. Found wanting means the pan did not come level: the thing weighed less than it should have.
How sure are we?
From the Book of Daniel, where the words appear on the wall at Belshazzar’s feast. The original Aramaic units are themselves weights, mene and tekel, which makes the passage a measurement metaphor in its own language.