Verify the dates and details of Jevons's Logic Piano — built 1869, exhibited before the Royal Society 1870 — against a primary or scholarly source

claim-jevons-logic-piano-1869-mechanical-inference-machine rests on Tier-4 Wikipedia for its two load-bearing dates: the machine was "built from his specifications in 1869" and exhibited before the Royal Society in 1870. Under the sources.md escalation rule, a surprising and load-bearing historical claim should not stay on a tertiary source.

What to read / pull:

• Jevons's own writings on the machine (his 1870 paper "On the Mechanical Performance of Logical Inference," Philosophical Transactions of the Royal Society) — the primary that would confirm both the mechanism and the 1870 Royal Society exhibition.
• A scholarly history of logic machines (e.g. Martin Gardner, Logic Machines and Diagrams) for the 1869 construction date and the Marquand connection.

What it gates: moving the note off seedling / clearing its [unverified-quant] flag. Also confirms the setup for observation-jevons-double-bridge-victorian-logic-machine-to-ai-energy.

Update 2026-07-12 (headless), from sibling capture 10-inbox/raw/2026-07-11-hop-jevons-logic-piano.md: two Tier-2 history-of-computing secondaries now corroborate part of this — the Rutherford Journal ("in 1869 he designed and built what is conceivably the world's first machine for doing logic inference … anticipated the contemporary computer by 80 years") supports the 1869 construction and the first-machine priority, and the Computer History Museum supports the elimination mechanism. Both are recorded in the note's corroborating_sources. This narrows the gap but does not close the question: neither Tier-2 source was independently re-fetched in the headless run, and the exact 1870 Royal Society exhibition date still rests on the paper's inferred venue (Phil. Trans. Royal Society) rather than the primary itself. Question stays open; what remains is the primary — Jevons's 1870 paper or the Royal Society record.

Separate, lower-priority thread (not gating this note): the Peirce→Marquand→Shannon electrical-switching lineage mentioned as context in the note rests on tertiary history-of-computing sites and would need Peirce's actual 30 Dec 1886 letter to Marquand to become its own claim. Left in the inbox as a lead, not routed here.