त्रिरज्जुकं निवर्तनमेकतः ॥ कZ_०२.२०.२३ ॥
trirajjukaṃ nivartanam ekataḥ
A nivartana is three rajjus on one side (i.e., defined by a side-length of three rajjus).
To define the unit by a measurable side-length in field conditions; it supports consistent area computation and prevents manipulation of irregular plots.