Scrupulum, meaning a tiny stone (from scrupus sharp stone), indicates a weight of 1⁄24 of a Roman ounce (i.e.) or, by extension, of other measures. Metaphorically, the stone is thought to be sharp and pricking, like a thorn.
As a weight or a coin, 1⁄24 of an uncia, or 1⁄288 of an as; i.e. 1.14 grams[1]
As a measure of land, 1⁄288 of a jugerum; i.e. about 9 m2 (97 sq ft)[2]
As a measure of time, 1⁄24 part of an hour, or 2+1⁄2 minutes.[3]
The forms scripulum, scriptulum, scriplus and scriptulus can be found, scriptulum being also associated with the lines on a draughtboard.