What is the earliest use of modern-day caste system in India? Where is this documented so I can reference it?
CLARIFICATIONS: These clarifications respond to questions and apparent confusions about what is a simple question. If there is no answer please say so. If down voting, please indicate your reasons. Since caste system is one of the great by-products of Hinduism, it is a valid topic of inquiry.
Modern-day, I meant as we currently understand. I wanted to exclude any ancient categories, such gods or demi-gods or other non-human categories. If I knew anymore about the evolution of castes, I probably won't be asking this question.
By documented, I meant justification for maintaining those categories into modern age, which includes recent colonial periods.
By reference, I meant any other resources besides bibliographic. I kept this deliberately open knowing Hinduism's strong oral tradition. It need not be restricted to scriptures or religious canons.