The kos miriam or “Miriam’s Cup” is a cup placed on the seder table next to Elijah’s. The cup — filled with water — honors the story of Miriam’s well, given to the Jewish people during 40 years of wandering in the desert. The photo at left is one example of a kos miriam.
I don’t think “Miriam’s Cup” has made it to most seders yet, but it is a lovely way of honoring women’s roles in the historic story of Passover. According to the Babylonian Talmud (Sotah 9b), “If it wasn’t for the righteousness of women of that generation we would not have been redeemed from Egypt.”
For more on feminist rituals during the seder, see here.