Verse
धूमेनाव्रियते वह्निर् यथादर्शो मलेन च ।यथोल्बेनावृतो गर्भस् तथा तेनेदमावृतम् ॥
dhūmenāvriyate vahnir yathādarśo malena cayatholbenāvṛto garbhas tathā tenedamāvṛtam
As a fire is covered over by smoke, as a mirror by dust, as an embryo is wrapped by the amnion, so this (knowledge) is enveloped by it.
Gītā 3·38