In the depths of human antiquity, the very first windows probably looked very much like the "shitajimado" (下地窓), brought back to life for use in the 16th century tea ceremony houses. 
The father of tea ceremony, Sen Rikyuu (千利休, 1522-1591) had noticed the rustic windows of the simplest rural farmsteads, and wanted to introduce this very simplest of windows to his tea house.
In the wattle and daub method of building, windows would be created by just not daubing (mud etc.) part of the wattle (bamboo, wooden sticks, reeds, etc), giving a reasonably structural strength while still allowing air and light to pass through.
This farmstead from around 1700 has a small shitajimado next to the hearth, the irori, to provide light and ventilation to the person tending the fire. The same general placement and use became standard in all tea ceremony houses built from the 16th century till today.
Some designs were very simple, with just the bare minimum and maybe a handsome wisteria vine tied around the vertical members, whether reed or cut stripes of bamboo.
The more the shitajimado was adapted outside of the spare tea house, the wilder it could get, with some very artistic designs, peaking in the 1920s.
Traditionally the idea is to use the wattle that makes up a wall so there was no use for a window frame, but some people want this type of window even in other forms of walls, and for them the design could be premade into a regular window frame and mounted as usual.
Many today are covered in glass panes or paper frames either hung or mounted as usual, but I still see some older buildings were people just nailed a square of mesh to keep bugs out.
Here is a modern western style teahouse built in the UK by Takeshi Hayatsu and Kristin Trommler and students of Cardiff University, using western timber framing, wattle and daub to create their version of Japanese tea house. Ample air and light by just leaving parts undaubed!
Sometimes we can build so much more by simple using so much less.
