Letters 108.32

When the scholar unrolls this same volume, he puts down in his notebook the forms of words, noting that reapse, equivalent to re ipsa, is used by Cicero, and sepse just as frequently, which means se ipse. Then he turns his attention to changes in current usage. Cicero, for example, says: “Inasmuch as we are summoned back from the very calx by his interruption.” Now the line in the circus which we call the creta was called the calx by men of old time.

Seneca, Letters to Lucilius 108.32, translated by Richard Mott Gummere