Miriam's cup is a new object added to the Seder.  Miriam was Moses's sister and rescued him from his basket in the Nile.  The scripture says, "I redeemed you from the house of slavery, and I sent before you Moses, Aaron, and Miriam" as she was there equal.  The Midrash says that, "just as Moses lead the men and taught them Torah, Miriam lead the women and taught them Torah, too."  As Elijah represents the future, Miriam symbolizes the past.  Miriam's cup is filled with water to honor Miriam's well.  Miriam would prophesize were the well would appear next in the desert so that the Israelites always had water to drink. 


haggadah Section: Hallel