Plutarch. Plutarch's Lives of the Noble Grecians and Romans
Englished by Sir Thomas North. Trans. Sir Thomas North. Vol. 6 (1579; London: David Nutt, 1896) 193.

     their lives, waying with him selfe the greatnesse of theMARCUS
     daunger: when he was out of his house, he did so frameBRUTUS
     and facion his countenaunce and lookes, that no man coulde
     discerne he had any thing to trouble his minde. But when
     night came that he was in his owne house, then he was
     cleane chaunged. For, either care did wake him against
     his will when he woulde have slept, or else oftentimes of him
     selfe he fell into suche deepe thoughtes of this enterprise,
     casting in his minde all the daungers that might happen:
     that his wife lying by him, founde that there was some
     marvelous great matter that troubled his minde, not beinge
     wont to be in that taking, and that he coulde not well deter-
     mine with him selfe. His wife Porcia (as we have tolde youProcia, Catoes
     before) was the daughter of Cato, whome Brutus marieddaughter, wife
     being his cosin, not a maiden, but a younge widowe afterunto Brutus.
     the death of her first husbande Bibulus, by whome she
     had also a younge sonne called Bibulus, who afterwardesBibulus booke
     wrote a booke of the actes and jeastes* of Brutus, extant atof Brutus
     this present day. This young Ladie being excellentlie wellactes.
     seene in Philosophie, loving her husbande well, and being
     of a noble courage, as she was also wise: bicause she woulde  Porcia
     not aske her husbande what he ayled before she had madestudied in
     some proofe by her selfe, she tooke a litle rasor suche asPhilosophie.
     barbers occupie to pare mens nayles, and causinge all
     her maydes and women to goe out of her chamber, gaveThe corage of
     her selfe a greate gashe withall in her thigh, that she wasProcia.
     straight all of a gore bloode, and incontinentlie after, a
     vehement fever tooke her, by reason of the payne of her
     wounde. Then perceiving her husbande was marvelouslie
     out of quiet, and that he coulde take no rest: even in her
     greatest payne of all, she spake in this sorte unto him: ‘IGreat differ-
     ‘being, O Brutus, (sayed she) the daughter of Cato, wasence betwixt
     ‘maried unto thee, not to be thy beddefellowe and com-a wife and a
     ‘panion in bedde and at borde onelie, like a harlot: but toharlot.
     ‘be partaker also with thee, of thy good and evill fortune.
     ‘Nowe for thy selfe, I can finde no cause of faulte in theePorcias
     ‘touchinge our matche: but for my parte, howe may I showewords unto
     ‘my duetie towardes thee, and howe muche I woulde doe forher husband
     ‘thy sake, if I can not constantlie beare a secret mischaunceBrutus.