We quantify the visibility drop of two-path interference as a function of recorded which-pathbits and present two experimental protocols that expose a sharp, reproducible “visibilitykink” predicted by the Principle of Least Information (PLI). We then propose and analyzea macroscopic Directional Zeno Ratchet: a repeated weak-measurement sequence produc-ing net drift with zero net classical impulse per cycle. Our framework is grounded in theJanus–PLI construction in which a Euclidean hidden-time influence yields a completely pos-itive, trace-preserving decoherence map and threshold-like suppression of off-diagonals oncean information cost is exceeded. We provide (i) cavity-QED and optomechanical protocols,(ii) an information-audit method (mutual information in bits vs. measured visibility), and(iii) quantitative “no classical impulse” bounds. Falsifiers are: absence of a visibility kinkand/or a ratchet that requires a nonzero classical force budget. The Second paper outlines he theoretical design of a relayivistic vehucle based on the Directional Zeno Ratchet