द्विहस्तं तोरणशिरः ॥ कZ_०२.३.२३ ॥
dvihastaṃ toraṇaśiraḥ
The head/top member of the gateway-arch (toraṇaśiras) is to be two cubits.
Uniform dimensions simplify procurement, reduce fraud in materials, and ensure structural consistency across state works.