A. Hamilton Thompson, The Historical Growth of the English Parish Church
“ The drain of the piscina was usually within the wall; but there are a number of twelfth century, and a few later, examples, in which the bowl forms a projection from the wall, and the drain was contained in a detached column, the base of which is frequently united to the foot of the wall. Projecting bowls are common, with drain-holes which slant downwards into the wall. A piscina is sometimes found in the sill of a window: one at Grantham is fitted with a removable drain, and there are other such examples. A drain in the chancel floor is sometimes found, usually of a rather early period. ”
