Between classical times and the tenth century we have little or no
guidance as to the art of calculation. Boethius (fifth century), at the
end of lib. II. of his _Geometria_ gives us a figure of an abacus of the
second class with a set of counters arranged within it. It has, however,
been contended with great probability that the whole passage is a tenth
century interpolation. As no rules are given for its use, the chief
value of the figure is that it gives the signs of the nine numbers,
known as the Boethian “apices” or “notae” (from whence our word
“notation”). To these we shall return later on.