Could Ancient Peruvians Soften Stone?

 Lying on the northern outskirts of the city of Cusco in Peru, lies the walled complex of Saksaywaman. The site is famed for its remarkable large dry stone walls with boulders carefully cut to fit together tightly without mortar.
The stones used in the construction of the terraces at Saksaywaman, which weight up to 150 tonnes, are among the largest used in any building in prehispanic America and display a precision of fitting that is unmatched in the Americas.
The stones are so closely spaced that a single piece of paper will not fit between many of the stones. This precision, combined with the rounded corners of the blocks, the variety of their interlocking shapes, and the way the walls lean inward have puzzled scientists for decades.

​The method used to match precisely the shape of a stone with the adjacent stones is still unknown, particularly as no tools were found in the vicinity of the site.
The “standard” explanation is that the Incans somehow managed to use a “guess and check” method of chipping at the stone with their stone tools, then setting the stone in place, seeing how it fit, then lifting it up and chipping further if it didn’t fit, then checking again, and so on.
However, considering the absolute precision of the cuts, shaping the blocks using only round stone hammers and repeatedly lifting up 100-tonne blocks to make adjustments throughout the process seems exceptionally unlikely.

Saksaywaman, in the history books, is said to have been completed in 1508, but those living just a few decades later, like Garcilaso de la Vega, born in 1539 and raised in the area of Saksaywaman, professed to having no idea about how the walls were constructed. And no one else seemed to either.
In fact, the Incans themselves acknowledged to the Spanish conquistadores that these structures were there long before them, built by different people. Is it possible that the Incans built on top of previously existing structures?
If the builders were even more ancient, it would mean that there was a civilisation much more advanced than the Incans, but of which we know almost nothing about—except that they could create structures like Saksaywaman.
One interesting theory that has been put forward to explain the shaping of the stones has its roots in local legend reported by explorers, such as the legendary Percy Fawcett, as well as Hiram Bingham, who rediscovered Machu Picchu. 
The legend speaks of a liquid derived from plants, which was known to the ancients to turn the stones soft. In fact, in 1983, a Catholic priest said he used the technique to achieve the stone softening but was unable to figure out how to make the stones hard again.

While the theory remains speculative, marks on some of the stones at Saksaywaman do indicate that the stones were moulded or scraped into shape, which could be explained by the stone softening theory.
Whether this theory proves correct or not is yet to be seen but it seems quite conclusive that the stone wall was not created with stone hammers and by repeatedly lifting up and down the massive stones.
As Ben Bendig from Epoch Times has said:
“Structures like this invite us to learn more about our past, and realize that the ancients might have been far more advanced than we give them credit.”