The Ebers Papyrus from 1550 BCE and the Kahun Papyrus from 1850 BCE have within them some of the earliest documented descriptions of birth control, the use of honey, acacia leaves and lint to be placed in the vagina to block sperm.[5][6] Another early document explicitly referring to birth control methods is the Kahun Gynecological Papyrus from about 1850 BCE. It describes various contraceptive pessaries, including acacia gum, which recent research has confirmed to have spermatocidal qualities and is still used in contraceptive jellies. Other birth control methods mentioned in the papyrus include the application of gummy substances to cover the "mouth of the womb" (i.e. the cervix), a mixture of honey and sodium carbonate applied to the inside of the vagina, and a pessary made from crocodile dung.