- A kind of early telescope.
1896, Orchard, Thomas Nathaniel, The Astronomy of Milton's 'Paradise Lost', London, New York: Longmans, Green, and Co., page 124:
- The instrument was at first called Galileo's tube; the double eye-glass; the perspective; the trunk; the cylinder.
1906, Strang, Herbert, In Clive's Command: A Story of the Fight for India, Illustrated, India: Bobbs-Merrill Company, page 115:
- He mounted, carrying the only perspective glass the vessel possessed. The captain watched him anxiously as he took a long look.
- (historical) An instrument for viewing an enlarged image of engraved prints or maps .