Research

http://mechanosynthesis.mit.edu/journals/001_ahslocum_pe_03_axtrusion.pdf

http://web.mit.edu/2.75/fundamentals/FUNdaMENTALs Book pdf/FUNdaMENTALs Topic 10.PDF

http://www.nelsonair.com/NA_primer.htm

Potential Materials

Granite Bar - https://www.amazon.com/Granite-Surface-Plate-18-Grade/dp/B006JYKIVC/ref=sr_1_3?ie=UTF8&qid=1484493918&sr=8-3&keywords=granite+surface+plate

claimed t be "Flat to 0.000025 inches" though I highly doubt that figure. I expect it to be ~0.0001