Water for aspersing worshippers was kept in an aspersorium, that those who entered or left the templo might dip their fingers into the water or be sprinkled by a priest. The same may be said of Indian pagodas, and the custom prevailed in ancient Egypt, and Etruria, with the Hebrews, and almost all the nations of antiquity. In Romo the priest used a small olive or laurel branch for sprinkling the people. Infants were also sprinkled with lustral water.
Source: Dictionary of Phrase and Fable, E. Cobham Brewer, 1894