D., Harvard Economic Studies, 1908, states on page 256 that: " ... both principal and interest were paid in full." Regarding the CPRR and Western Pacific RR, Tutorow, p.
1004 reports that final payment to the government was organized by a commission appointed by an 1898 act of congress, determined to be ,812,715.48 on Feb.
Not a scientific way to calculate but as close as you will ever get for just the rail.
Using that method of measurement the Central Pacific railroads 690 miles of track would have been approximately 69,000 (metric tons 2240#) tons of rail.
See the discussion of "dollars per mile of track" including the question of exactly where do the Sierra Nevada mountains begin and end. Graves states that the 1887 Pacific RR Commission said the cost of construction from Sacramento City to Promontory, as of July, 1869 was ,249,916.11; cash or cash equivalent was ,397,135.58.
See comments regarding the role of the government in financing the transcontinental railroad. The bonds were sold at par in New York, then transferred to San Francisco where they were converted to cash/gold.
If the rail is 56 lb/yard, then the total rail weight is about 175 thousand tons (about a hundred tons of rail per mile).
To this you would need to add the weight of about 5,500 spikes and 1,408 bolts per mile, 900 tons of iron used in the construction of the Sierra snow sheds, plates, switches and sidings, iron hardware used in constructing wooden trestle bridges, 20-40 ton locomotives, cars, etc.