Natyashastra
शैलयानविमानानि चर्मवर्मायुधध्वजाः । मूर्तिमन्तः प्रयुज्यन्ते नाट्यधर्मी तु सा स्मृता ॥ ७६॥
The use of material objects like mountain-carriages, aeroplanes, shields, armaments, and flags, which are applied in a tangible form, is considered in accordance with the principles of drama.
english translation
zailayAnavimAnAni carmavarmAyudhadhvajAH । mUrtimantaH prayujyante nATyadharmI tu sA smRtA ॥ 76॥
hk transliteration by Sanscript