According to Don Rosebrook's excellent resource book American Levels and their Makers, the first levels, which consisted of an A-frame and plumb bob, were developed by the ancient Egyptians.
Early Romans devised an instrument that's the ancestor to the type of level we're familiar with today. They used a flat-bottomed trough containing water. When the water reached the same level along the inside walls of the trough, the device would be level. Simple, but effective.
The use of a tube filled with fluid (wine, in this case) and an air bubble dates back to the 1600s and is credited to Dr. Robert Hooke, an English philosopher.
The levels that are featured in Rosebrook's book are primarily mid to late 19th century. Woods used during that time include beech, boxwood, cherry, ebony, mahogany, rosewood, and others—heavy, dense, and stable wood. High-end levels were made of rosewood and often had the most metal trim, some of which was ornate.
This is where my level comes in. Like many women, I like shiny things. But not so much on my fingers or ears as on my tools.
I spied what I think is probably a craftsman-made level (because of its shape) in Tony Murland's collection, and decided it was "the one." A tiny image and one measurement (length) is my reference. Based on this I'm making my level with a .125" strip of brass and a cherry blank. The final dimensions will be 1.5" thick (inlcuding the brass) x 1.75" wide x 10.5" long.
I cut the brass on my new scroll saw (a stress-shopping purchase) with metal-cutting blades, filed it smooth, and screwed it to the cherry blank.
The next steps will be to cut the mortise for the vial, cut the blank to shape, add brass corners to the bottom, and mount the vial.
This is a very fun little project which should get some use in my shop. It would also make a nice gift for someone who likes shiny things.
Valentine's Day is just around the corner, after all.
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Thank you to the commenters who found some helpful links:
Machinists' center drill for starting screw holes in brass.
Slotted brass screws.
More slotted brass screws.
Thread about replacing level vials.
Level vials.