षट्त्रिंशदङ्गुलमञ्जनवर्णं सामूरम् ॥ कZ_०२.११.८९ ॥
ṣaṭtriṃśadaṅgulamañjanavarṇaṃ sāmūram
Sāmūra is (specified as) thirty-six aṅgulas (in measure) and of the color of collyrium/antimony (dark black).
It standardizes acceptance and pricing, prevents under-delivery, and simplifies auditing of storehouse issues and workshop consumption.
Color is a quick inspection proxy for processing method, dyeing, and grade; it helps detect substitution or defective curing.