Two twinklings of an eye

Mar Samuel, the great Hebrew polymath of Nehardea in Babylonia (165-257) reckoned 56. 848 atoms to the hour, the hour, one atom (rega’) being equivalent to two twinklings of an eye (heref ‘ayyin).*

* Needham, Joseph: Science and Civilisation. Vol.4 (Physics and Physical Technology), Part 1, Cambridge: Cambridge University Press, 1962, p.4

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