Charak Samhita
आयुःप्रदान्यामयनाशनानि बलाग्निवर्णस्वरवर्धनानि। मेध्यानि चैतानि रसायनानि मेध्या विशेषेण चशङ्खपुष्पी ॥३१॥
these Rasayana drugs are life promoting, disease alleviating, promoters of strength, agni, complexion, voice and are intellect promoting. Of them shankhapushpi is specifically intellect promoting.
english translation
AyuHpradAnyAmayanAzanAni balAgnivarNasvaravardhanAni। medhyAni caitAni rasAyanAni medhyA vizeSeNa cazaGkhapuSpI ॥31॥
hk transliteration by Sanscript