Optician Achim Leistner hand-polished the Avogadro Project's silicon spheres, using a tactile technique nicknamed 'atomic feeling'

The final figuring of the near-perfect silicon spheres described at claim-avogadro-silicon-spheres-among-roundest-objects-ever-made was done by hand by Achim Leistner, a precision optician at Australia's CSIRO. According to the Powerhouse Museum's object record, Leistner trained at Zeiss in Jena (qualifying as a precision optical craftsman in 1953) and emigrated to Australia in 1957; on the sphere project he relied on "precision handcrafting, to ensure minimisation of any irregularities" and, beyond his instruments, on "his hands to feel for any imperfections in the surface of the spheres." The research team nicknamed this manual technique "atomic feeling," and the museum states it "proved superior to purely machine-based methods."

That last claim — that unaided fingertips outperformed instrumented polishing at the nanometer scale where these spheres are figured — is surprising and load-bearing, yet rests on a single Tier-3 museum record; it is held at seedling and flagged pending Tier 1–2 corroboration, tracked at question-verify-leistner-atomic-feeling-superior-to-machines.

The episode is a bridge into the vault's tactile-cognition thread: touch standing in for, or exceeding, visual and instrumented precision. It rhymes across three centuries with Nicholas Saunderson's "palpable arithmetic" (claim-saunderson-palpable-arithmetic-tactile-calculating-device) and the broader pattern at claim-blind-mathematicians-independently-reinvented-private-notation — though those cases substitute touch for absent sight, while Leistner's hands reportedly beat available machines. Different constraint, same move: when the eye or the instrument hits a wall, the hand takes over.