[muir_redwoods]

Measuring existing relics in 1870 in no way accounts for all the pieces bought and sold over the centuries; many such pieces could have been destroyed, lost, discarded as fakes etc. over the years

[agere_contra]

Of course. De Fleury measured the known pieces. They came to 0.004 cubic meters - which is about 1/50 of a cross.

Even if ten times as many pieces had been lost, burnt by Saracens etc - that takes the tally to 1/5 of a cross.

That's ... a pretty small forest. And that's all that the historical record actually tells us. Anything else is unfounded conjecture.