Spirals and track precision on narrow gauge lines

After reading many engineering pages about laying out track work, especially for spirals on curves, I look back at the blue print plans for the Sumpter Valley RR and spirals are not shown... just a straight approach to a constant degree curve. Is/was this common practice to not show spiral easements to curves on blueprints or were they luxuries not found on smaller rail lines. I figure for logging railroads, tracks were laid down and directed anywhere needed but I would expect a mainline to be a bit more formal. If spirals were used (but not shown) would anyone care to offer an opinion for what the rule of thumb was to lay them out. Some texts suggest that a chord should be divided into 10 segments with the first and last two segments with curvatures at a half (segments 2 and 9) and one quarter (first and last segments) of the chord curvature.
thoughts and/or comments?