Pliny the Elder, Natural History 35.109
Pliny is discussing a painter by the name of Nicomachus.
nec fuit alius in ea arte velocior. tradunt namque conduxisse pingendum ab Aristrato, Sicyoniorum tyranno, quod is faciebat Telesti poetae monimentum praefinito die, intra quem perageretur, nec multo ante venisse, tyranno in poenam accenso, paucisque diebus absolvisse et celeritate et arte mira.
There was no one else swifter in that art. For they say that he took a commission from Aristratus, tyrant of Sicyon, to paint a monument which he was making for the poet Telestes, and they agreed a date for its completion; Nicomachus arrived not much before that date, by which time the tyrant had become angry and was threatening him with a penalty. Within a few days he carried out the work with astonishing speed and skill.