Lattice ('gelosia') multiplication's paper trail runs India (12th-c. Lilavati commentary) → Islamic Maghreb (Ibn al-Banna, late 13th c.) → Renaissance Italy

Lattice (or gelosia) multiplication — reading the partial products of a long multiplication off a diagonal-ruled grid — has a documented transmission history that predates the European devices built on it (see claim-napiers-bones-hardware-wrapper-on-lattice-multiplication). As recorded in tertiary sources, the method's paper trail has three legs:

1. Indian precedent (12th c., partially attested). A method called Kapat-sandhi, described as "very similar to the lattice method," appears in a commentary on the 12th-century Lilavati of Bhāskarāchārya (Bhāskara II).
2. Islamic Maghreb (late 13th c., first full description). The earliest full description in Arab mathematics is attributed to Ibn al-Banna' al-Marrakushi in his arithmetic treatise Talkhīṣ aʿmāl al-ḥisāb ("Summary of arithmetical operations"), written in the Maghreb.
3. Renaissance Italy. The method arrived in Europe as gelosia, later packaged by John Napier into the physical rods of his 1617 "Napier's bones."

The route — Indian origin, an Islamic-world intermediary that carries the surviving transmission, European arrival under a new locally-meaningful name (see claim-lattice-multiplication-renamed-window-grille-in-arabic-and-italian) — is structurally identical to the path traced for a wholly different kind of material at claim-kalila-wa-dimna-descends-from-borzuyas-lost-pahlavi (a Sanskrit fable collection → lost Pahlavi → surviving Arabic → Europe, carried by Borzuya, claim-borzuya-immortality-herb-was-really-a-book). Two unrelated domains — an arithmetic technique and a fable collection — moving India → Islamic intermediary → Europe on nearly the same multi-century schedule is the cross-domain pattern this capture was promoted to preserve, pursued further at question-transmission-chains-renamed-for-local-resemblance-pattern.

Why this note is seedling and flagged. The route is uncontested in outline, but it is the load-bearing point of the note and rests only on Tier 4 Wikipedia, and its dates are quantitative claims floored at Tier 1–2. Two specific attributions — that the lattice method actually sits inside Ibn al-Banna's Talkhīṣ, and that Kapat-sandhi is genuinely the same technique — are unconfirmed above the encyclopedia floor and routed at question-verify-lattice-multiplication-maghreb-india-primary.