As part of a major study of the conservation of degraded historic textiles, several mechanical and physical properties have been measured on archeological cotton mortuary wrapping cloths removed from Peruvian mummy bundles. Data is presented for yarn structure, count, twist, helix angle, twist factor, crimp and tenacity. Yarns from different mortuary wrappings were surprisingly similar in construction and mechanical properties. High twist two-ply yarns were formed from relatively low twist singles resulting in a loss of the bulk observed in the singles yarns. A numher of the yarns had helix angles from 40 to 50 degrees. This degree of twist no doubt contributed to the good strength observed in these eight hundred year old yarns. Weave crimp data indicate that the plain weave fabrics are warp faced.