" Fingers of bitumen Here we have to understand the measure as the Sumerian ideogram ŠU.ŠI (usually written ŠU.SI), standing for the Babylonian ubānu, ‘finger’, one of which comes out at about 1.66 centimetres. Bitumen is thus applied to all ark surfaces to a depth of one finger. "

― Irving Finkel , The Ark Before Noah: Decoding the Story of the Flood