According to Houbraken when he returned from Italy he had with him a copy he had made himself after Nicolas Poussin, which the postmaster of Zwolle bought without asking him who had painted it.
[1] When Isaac later declared that it was a copy by his own hand, he claimed the postmaster had never explicitly asked who had painted it, but had wished to see his things that he had brought back with him.
[1] This anecdote was told in order to show the popularity of Poussin in the art market of the Netherlands in Gerard Uilenburg's time.
Moucheron told Houbraken that he judged De Molijn at that time to be a man of about 50 in 1697.
[2] Houbraken intended to write a biographical sketch of Isaac in his birth year of 1667, and mentioned this in his biographical sketch of his father Frederik de Moucheron, but was unable to complete it (he died before publication of Volume III, which ended with birth year 1659).