In a letter to Francesco Vettori Machiavelli famously wrote:
When evening comes, I return home and go into my study. On the threshold I strip off my muddy, sweaty, workday clothes, and put on the robes of court and palace, and in this graver dress I enter the antique courts of the ancients and am welcomed by them, and there I taste the food that alone is mine, and for which I was born. And there I make bold to speak to them and ask the motives of their actions, and they, in their humanity, reply to me. And for the space of four hours I forget the world, remember no vexation, fear poverty no more, tremble no more at death: I pass indeed into their world.
Although not definitive, this suggests that his well known portrait by Santi di Tito might have had him attired in "the robes of court and palace", possibly even of his own design. The style is vaguely reminiscent of a black clerical rabat worn over a red alb, such as is still sold in liturgical clothing stores.