Leitz Compound Light Microscope and Nachet Camera Lucida
The above image is a Quicktime VR virtual object that can be rotated and the camera lucida mounted by dragging your courser left or right, up or down. On a track pad a two finger drag works very well.

This is a Leitz Compound Light Microscope with a triple objective nose piece. This scope was from the 1899 to 1903 period. There is a substage condenser and iris. The Nachet Camera Lucida works very well with this microscope, it simply replaces the ocular and the prism allows you to see the table top to the side of the microscope (lefty or righty) and the image of the specimen when you look through the eye piece. This double image allows you to trace the image of the specimen on a piece of paper on the table.

This work takes a little practice, but it is very rewarding and sharpens your observational skills. The big trick here is balancing the brightness of the two images. If one it too bright it will dominate the view and you will not be able to trace. The brightness is adjusted by using the substage iris, a blue filter which can be placed over the mirror, or adjusting the light source for the table or the stage specimen.

I will try to work on a photo through this eye piece and some others to help with this explanation. These things are really amazing tools. They are still used today in various designs to illustrate characteristics of organisms as part of the species description process at the museum where I work.