Telescopes. Primary Documentation, you can't beat it.

So it seems that small telescopes were used in the mid 18th century, even though this person appears to be looking through his telescope backwards !

Drawing of a sailor, Louis Philippe Boitard, mid-18th Century, British Museum.

The author's replica telescope with a crude leather wrap & leather carry pouch.

A Scouting & Ranging Link.

http://ranger-pathfinder-notes.blogspot.com/2011/03/how-to-scout.html?showComment=1299470435383#c2368965833077848438