Simplify the following text for a Grade 9 native English-speaking person.
Original: This cubit is sometimes referred to as a `` natural cubit '' of 1 Â 1\/2 feet and was used in the Roman system of measures and in different Greek systems .
Simplified: This so-called `` natural cubit '' of 1 Â 1\/2 feet is used in the Roman system of measures and in different Greek systems .