The piece nobody has written yet — because they'd need to have read all three of the vault's big yoga-history books in the same week — is this: every history of yoga is a history of either the idea or the man, and almost none is a history of the substance the man actually worked.
It hit me finishing the Alchemical Body deep ingest, holding it next to Samuel and Sinister Yogis. Samuel tells you when the subtle body appeared (8th–10th c.). Sinister Yogis tells you who the yogi was (a power-seeker, a body-snatcher, reinvented in the 1930s). And both leave a hole exactly where the practice lives — neither tells you what the yogi did with his hands, what he held in his mouth, what he was trying to keep from falling. White's first volume fills it: he was working mercury, semen, and breath, and haṭha-yoga is that work turned inward. Marco Polo and Bernier both described yogis drinking mercury for breakfast, and the historians of yoga have been quietly embarrassed by it for a century, because a meditator who drinks quicksilver looks like a category error. He isn't. He's the operative yogi, and he's been hiding in plain sight.
The wire that holds: the operational vantage is a distinct question that scholarship structurally drops, and recovering it (alchemy) doesn't just add to yoga's history — it shows that what we call "yoga" today is the substance-stripped remainder.
Same domain: this extends Alchemy as the Missing Substrate and the three-histories frame in White's Trilogy Architecture. It pulls against Krishnamacarya 1930s Reinvention — the essay would argue the 1930s reinvention is specifically a de-operationalization. Cross-domain, it touches the history-of-science principle that the operational layer of any craft is the under-recovered one.
Essay seed: "The Operative Yogi." The angle nobody's written: read the history of yoga as a three-vantage problem (when / who / what-operationally), show that the operational vantage — alchemy, mercury, sexual fluids, breath-as-the-fixing-of-a-volatile-precious-substance — is the one the histories drop, and argue that modern yoga is the operative yogi with his materials confiscated. Audience: serious yoga practitioners and historians; what they'd resist is the claim that the "ancient" practice they revere is the de-operationalized residue and the real ancient thing involved eating mercury. You'd need: the three-book synthesis (have it), the Krishnamacarya reinvention argument (have it), and ideally Kiss of the Yoginī for the sexual-fluid connective tissue (don't have it yet — the known gap).
Collision candidate: the operative-yogi reading vs the practitioner-lineage warrant's "living ancient tradition." Already partly held in the Vivekananda-vs-White and White-vs-Iyengar collisions.
Concept page: possibly "the de-operationalization of modern yoga" if a second source touches it.
[ ] A second source touches this independently (candidate: Kiss of the Yoginī, or a modern-yoga-history source) [ ] Has survived two sessions without weakening [x] The Live Wire second framing holds (the three-vantage structure) [x] Has a falsifiable core claim (modern yoga = de-operationalized residue — testable against the actual content of 1930s sources)