In the Qumran community, the Essenes created several cisterns that, as shown here, were plastered and had steps to allow them to access water. At least two of these cisterns are believed to be mikvoth, ceremonial or ritual baths used for actual cleansing.
Impurity resulted from a variety of conditions, some of which are listed in Numbers 5:1-4 (e.g., touching a dead body, having a skin disease or issue of body fluid). More important, these baths indicated the spiritual cleansing the resulted from repentance and forgiveness (Matthew 3:6, 11).
The Essenes apparently believed that any breaking of God's law required cleansing, which the mikvoth symbolized. While there are several Jewish practices that provide a foundation for baptism, the Essene mikveh practice certainly contributed to our understanding of the meaning of the ritual cleansing.