measure, amount

量 is composed of 日 (sun) and a variant of 東 (east). The sun rises in the east, making it the optimal direction for observing the sun. Ancient people calculated the timing of agricultural activities by observing the sun, so 量 means estimation or measurement. Additionally, observing the sun aided farming, so 量 also extended to mean food or provisions, but this meaning was later taken over by the character 糧 (grain).