De Missy spent his life collecting manuscripts for a new edition of the New Testament. Some manuscripts he brought from
Mount Athos (e.g.
British Library, Add MS 4949). To his collection belonged the manuscripts of the New Testament
449,
483,
560,
561,
ℓ 38,
ℓ 162,
ℓ 239,
ℓ 240,
ℓ 241, and other. Afterwards the collection belonged to
William Hunter, then to
Matthew Baillie (1761–1823), and finally it came to the
Glasgow University in 1807. ==Personal life==