तस्यापिहितकाचकस्योदके निमज्जत एकदेशः सीदति पटलान्तरेषु वा सूच्या भिद्यते ॥ ॥
tasyāpihitakācakasya udake nimajjata ekadeśaḥ sīdati paṭalāntareṣu vā sūcyā bhidyate
For that object sealed with a glass cover: when immersed in water, one part sinks; or, between the layers it is pierced with a needle (to test).
They are quick, low-cost, and reproducible—ideal for routine enforcement by inspectors without specialized equipment.