The paper ladder

Claim (verbatim)

The paper ladder. This connects paper-trade standardization with the size distribution of surviving books. Paper left the mill in named full-sheet formats, and books were cut as the full sheet, its half, its quarter, its eighth; a warraq's stock was a ladder, not a continuum. If the trade was standardized, extant manuscript heights should be multimodal, with discrete rungs at fixed ratios generated by successive folds of a roughly 2:3 sheet, and with genre sorted onto the rungs, display Qurʾans and presentation copies at the top, personal taʿliqa notebooks at the bottom, because decorum and price both scaled with the rung.

Prediction clause (verbatim)

Heights of dated Islamicate paper manuscripts from 700 to 1600 CE form a multimodal distribution: a dip test rejects unimodality at p<0.01, at least four modes appear, and adjacent-mode height ratios fall between 1.25 and 1.55 (the alternating ratios of repeatedly folding a 2:3 sheet). Primary clause: rejection of unimodality with at least four modes; the verdict follows it. Secondary: the adjacent-ratio window and the genre sorting across rungs.

Kill-dataset (verbatim)

Kill: FIHRIST, which records height and width in millimetres for thousands of dated Islamic manuscripts in UK collections.

Novelty / leakage triage

provisional — model-triaged, shepherd review pending

A provisional first pass authored by the model (Opus), not yet confirmed by the shepherd. It carries the same dated-search requirements as an authoritative verdict but is excluded from every headline figure and cannot underwrite a prediction until a shepherd confirms it. Provisional reading: Adjacent (closely related prior work exists).

The premise is documented: paper left the mill in named full-sheet formats (Baghdadi and other city-grades, some designating large sheets), and books were cut as the full sheet or its fractions -- codicologists reconstruct original sheet sizes from surviving leaves, and Humbert's and Bloom's work maps format standardization and chain-line groups. Not located: the item's specific distributional test -- dated Islamicate paper-manuscript heights (700-1600 CE) rejecting unimodality (dip test p<0.01) with >=4 modes at adjacent ratios of 1.25-1.55 (successive folds of a ~2:3 sheet), plus genre sorting across the rungs -- run over the FIHRIST height field. Format standardization is established; the multimodal fold-ladder measurement is unrun.

• Jonathan M. Bloom, Paper Before Print: The History and Impact of Paper in the Islamic World (Yale, 2001); Genevieve Humbert on Islamic paper formats/chain-lines — Named full-sheet formats, city-grade sizes, and cutting books from full sheets
• FIHRIST dated-manuscript records (height/width in mm) — The kill dataset for the multimodal height (dip-test) analysis

Predictions

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