Abstract

Starting point of this article is a problem obvious to anybody who reads the medical papyri of ancient Egypt from the New Kingdom and the Late Period: the prescriptions contain two dyadic systems of notation for measures of capacity without specifying the unit of measurement, firstly the Horus eye fractions 1/2, 1/4, 1/8, 1/16, 1/32 and 1/64 which are unanimously assumed to refer to the single Heqat and secondly the ‘normal’ dyadic fractions from 1/2 to 1/128, which have been interpreted in widely different ways, as fractions of the Henu‐, the Ro‐, the single Heqat‐, the 5‐Ro‐ or the Dja‐measure, respectively. Interpretations suggested in translations and commentaries have remained inconclusive and unsatisfactory. Based on new findings and readings, the present study sets out to show that•the hieratic Horus eye fractions in the medical papyri of the New Kingdom and the Late Period refer to the quadruple and not to the single Heqat;•the ‘normal’ fractions refer to the smallest Horus eye fraction 1/64 quadruple Heqat which corresponds from the New Kingdom (at the latest) to 1 Dja;•the units Dja and Henu are in a ratio of 5:8 and not of 2:3, this unusual ratio of 5:8 makes sense in Egyptian thought when expressed as 40:64; 40 Henu (= 1 Oipe = 1 quadruple Heqat) equal 64 Dja and therefore the complete Horus eye, the smallest fraction of the Horus eye, 1/64 is 1 Dja;•hence, the capacity markings of the two complete vessels known to exist with marked volumes of 1 and 1/2 Henu and 1, 1/2, 1/4, 1/8, 1/16, 1/32 and 1/64 Dja, allow all relevant volumes to be measured which are required in the preparations mentioned in extant medical papyri.