I used to have a wooden frame over the table (ideally, you'd mount it on the wall, on something like a wall TV mount to avoid any vibrations), about 1m above, a 55-200mm lens and macro extension rings.
Only thing I was lacking was decent lighting, LED's were still pretty expensive at the time and incandescent was too how for dissecting flowers.
If I can get my hands on the macro rings, I'll sit some footage tomorrow and post it.
Edit: I didn't get 400x magnification with that lens mounted that high but that's only a matter of distance and focal length.
Edit, again: one good trick to get good magnification is to mount a lens backwards.