Charak Samhita
मूत्रस्रोतःपरीणाहं मुद्गस्रोतोऽनुवाहि च। अपत्यमार्गे नारीणां विधेयं चतुरङ्गुलम्॥६६॥
It should be introduced to a length of 4 angulas in the genital tract and 2 angulas into urinary tract for adult females and 1 angula for bala (unmarried below 16 years of age).
english translation
mUtrasrotaHparINAhaM mudgasroto'nuvAhi ca। apatyamArge nArINAM vidheyaM caturaGgulam॥66॥
hk transliteration by Sanscript