Haak's correspondence with Mersenne dwindled after 1640; Haak had diplomatic engagements in Denmark, and had started on his more ambitious translation work, including an English translation of the Dutch Annotations upon the Whole Bible.
Haak died on 9 May 1690, at the home of Frederick Slare, a friend, cousin and F.R.S., in the Fetter Lane area of London [REF].