A certain 'dharmic' religion burned widows alive on their husbands' funeral pyres unto well into the 19th century.
Many a times, the widows chose to go with their spouses, sometimes it was for the fear of being dishonored by Muslim invaders. RigVeda mentions of a brother of a deceased person exhorting the wife to leave the pyre and return to world. In early British rule in Eastern India, especially in Bengal, widows were pushed into the pyre to usurp the property of the deceased. This was the effect of British laws and consequent materialism. The old traditions had broken up.
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Between 1815 and 1818, the number of incidents of sati in Bengal doubled from 378 to 839. ..
The archaeologist Elena Efimovna Kuzmina has listed several parallels between the burial practices of the ancient Asiatic steppe Andronovo cultures (fl. 1800–1400 BCE) and the Vedic Age. She considers
sati to be a largely symbolic double burial or a double cremation, a feature she argues is to be found in both cultures, with neither culture observing it strictly. ..
According to Romila Thapar, in the Vedic period, when "mores of the clan gave way to the norms of caste," wives were obliged to join in quite a few rituals but without much authority. A ritual with support in a Vedic text was a "symbolic self-immolation" which it is believed a widow of status needed to perform at the death of her husband, the widow subsequently marrying her husband's (eligible) brother.
According to
Ashis Nandy, the practice became prevalent from the 7th century onward and declined to its elimination in the 17th century
to gain resurgence in Bengal in the 18th century.
Colonial era revival:
Sati practice resumed during the colonial era, particularly in significant numbers in colonial Bengal Presidency. Three factors may have contributed this revival: sati was believed to be supported by Hindu scriptures by the 19th century; sati was encouraged by unscrupulous neighbours as it was a means of property annexation from a widow who had the right to inherit her dead husband's property under Hindu law, and sati helped eliminate the inheritor; poverty was so extreme during the 19th century that sati was a means of escape for a woman with no means or hope of survival.
Daniel Grey states that the understanding of origins and spread of sati were distorted in the colonial era because of a concerted effort to push "problem Hindu" theories in the 19th and early 20th centuries. Lata Mani wrote that all of the parties during the British colonial era that debated the issue, prescribed to the belief in a "golden age" of Indian women followed by a decline in concurrence to the Muslim conquests. This discourse also resulted in promotion of a view of British missionaries rescuing "Hindu India from Islamic tyranny". Several British missionaries who had studied classical Indian literature attempted to employ Hindu scriptural interpretations in their missionary work to convince their followers that Sati was not mandated by Hinduism."
Sati (practice) - Wikipedia
This in present age is known as 'chadar dalna' and was prevalent in North India till very recently. Of course, now the law permits the marriage of a widow freely.