[5] He studied the works of classical authors on history, philosophy, and science, including mathematics from Frans van Schooten.

In 1649–1650 Huygens accompanied Adriaen Pauw to England [6] and toured through Belgium, France, Switzerland and Italy.

During the Nine Years' War, Constantijn left for the Southern Netherlands each spring, returning to London each autumn.

Around 1650 when Christiaan Huygens became interested in microscopes and telescopes, Constantijn helped him with the construction of the lenses.

He presented a 7.5 inch (190mm) diameter 123 ft (37.5 m) focal length aerial telescope objective to the Royal Society in 1690[13] that still bears his signature.

[17] The book includes chapters on such subjects as the changing perception of time, book collecting, Huygens's role as connoisseur of art, belief in magic and witchcraft, and gossip and sexuality at the court of William and Mary.

[19][20] Huygens Jr. made some drawings and paintings, depicting this castle in the period between 1650 till 1660.

[22][23] The latter Constantijn received in 1690; he mended and mounted it, believing it to be a Leonardo original, though it is more likely by either Bernardino Campi or Carlo Urbino.

[24][25] According to Huygens, Romeyn de Hooghe illustrated La puttana errante, an erotic book by Pietro Aretino.