My teacher said that the Sati practice was not actually a common practice and does not belong to our dharma. Vedic Religion was there from around 500 BC but Sati started from around 4th century (I forgot the number but I guess it was 4th). She also mentioned that at that time widows were seen in bad light and usually after wars (like in Rajput wars) widows were tortured physically and sexually. Also widows were expected to marry their husbands' younger brother. So the widow will voluntarily jump in to fire of her dead husband.
But I also saw someone commenting:
Sati is not a questionable practice. It is the greatest display of chastity a woman can show toward her husband, and since chastity comes from the mind, it is only true if it is voluntary. It is also religious, because it is accepted by shastras and they mention phalan (great rewards) for this act. It is not 'merely cultural'
So my question is where in our texts is Sati mentioned? Also, except sati devi, is there anyone who performed sati?
This is not a dup. of the other question What is the truth behind the practice of Sati? How is it related to Hinduism? There, the asker wants to know the truth behind Sati system. The top-voted answer there doesn't cite any sources and goes on to say that Sati is a cultural practice and not a religious one. This question however is looking for scriptural sanction for Sati and some real examples.