Three pages in this vault describe the same experience, and none of them knows the other two exist.
As a technique. Start at the crown and work down, taking the material out as you go. What is left is a transparent balloon full of light, loose as a sack, because all your bones have melted away — and there is not a single barrier in your body that can block the chi or mai. Something to do, deliberately, tonight.
As a marker. The body feels like an empty sack with nothing inside, with the skin still there as an outer wrapping layer. It arrives on its own, in the state that immediately precedes the first dhyāna, and it is the one you must not miss.
As a marker with a technique's name. Your bones feel as if they have dissolved and your body feels like an empty sack. It is called empty shell meditation. And: such sensations never last long.
[RESONANCE] The third one is the tell. Somebody attached the word meditation to something described as happening by itself, and nobody in three books noticed the two accounts had collided.
But the thing that actually stops you is the second-order problem. If the empty sack can be produced on purpose — and one of these pages gives step-by-step instructions for producing it — then feeling it is no longer news about anything. A practitioner who has read the balloon page has permanently disabled the marker for themselves. Not misread it. Destroyed it, by acquiring the ability to make it.
The vault holds a great many diagnostic markers of this kind, and almost all of them are stated as sensations. Coolness in the soles. Warmth at the navel. Sweet saliva. The top of the head opening like sun through a window in spring. Stars visible in daylight. Every one of those is presented as evidence because it arrives unbidden.
And the same corpora that publish the markers also publish the visualisations. The Empty Balloon says the exercises are endless and interchangeable — swap the balloon for a skeleton, a flame, a Buddha at the crown, and nothing important changes, because the picture was only ever a place to put attention.
So the corpus is simultaneously running a diagnostic system and a system for manufacturing its readings, and the two are printed within pages of each other with no fence between them.
Against Ching-An, the Precursor State and The Baptismal Gongfu, which both treat the empty sack as a reading taken in passing — and against This Is Not Sainthood, where the whole refrain depends on the phenomena arriving rather than being made.
The sharp version: a tradition that publishes both its diagnostics and its methods has an unacknowledged contamination problem, and the more complete the publication the worse it gets. Which would be an argument for the secrecy this corpus spends its tantra chapter complaining about — and the corpus never notices that it has made one.
Promotion criterion: find one tradition that fences the two apart deliberately — that names a marker and says this one you must not practise toward. If nobody does, the observation is real and nobody has drawn it. If somebody does, that fence is the page.
Sweep the vault's marker pages for any that carry a manufacture warning. ching-an-the-precursor-state, the-three-fullness-signs and three-flowers-and-the-literalism-hazard are the three most likely to have one, and the last of them already argues that its phrase gets read as an instruction — which is the same defect one step earlier.