Foucault knife-edge test - Wikipedia

Ego-Libertarian Marxism - Polcompball Anarchy Wiki

foucault Guy's Math & Astro Blog

Foucault test: a quantitative evaluation method

Optics Guy's Math & Astro Blog

Does the bob (weight) of a Foucault pendulum keep its orientation with the direction of swing, with the room that it is in, or neither? - Quora

Foucault test

Schlieren - Wikiwand

Traditional Foucault apparatus influence on analysis - ATM, Optics and DIY Forum - Cloudy Nights

The Ronchi Test -- What it Measures and how Sensitive is It? - Page 2 - ATM, Optics and DIY Forum - Cloudy Nights