Introduction

Κατὰ δὲ Πρωταγόραν τὸν σοφώτατον πάντων χρημάτων ἄνθρωπον μέτρον εἶναι, κατὰ δὲ Θεαίτητον τούτων οὕτως ἐχόντων αἴσθησιν ἐπιστήμην γίγνεσθαι (the doctrine of the great philosopher Protagoras, that man is the measure of all things, and the doctrine of Theaetetus that, since these things are true, perception is knowledge) (Platon, Theaetetus 160 d.9). This quotation may perhaps bring to mind the Egyptian cubit, of the length of a human forearm, and its subdivisions into palms and digits. In architecture, ergonomic requirements, such as the height of a door or the measurements of a staircase, exhibit dimensions related to the human body, whose nature makes them universal and diachronic (cf. Palyvou 2005, 156 with reference to Modular Man by Le Corbusier). The technique of measurement by weight is very close to Theaetetus's doctrine that perception leads to knowledge, since everyone can feel which is the heavier of two objects held in the two hands. Thus the mechanism of the balance, which actually predates the invention of weights, in fact reproduces an action performed by the human body itself. In the tomb of Ka-irer, dating to the Old Kingdom of Egypt, there is a scene showing ingots being weighed in a curiously designed balance in the form of woman with arms stretched horizontally (Kisch 1965, 26; Lauer 1976, 77). Furthermore, the most widely occurring largest unit in various metric systems is the heaviest load that a man can comfortably carry on his shoulders, that is, about 30 kilos (Figure 7.1).