Our guide at the MachuPicchu quarry explains how the Inca stonemasons chipped rectangular slots then hammered in wedges, or allowed water to freeze and expand, to split the stone.
MachuPicchu quarry. The piece on the ground has been split off, about 500 years ago, ready to be painstakingly shaped and fitted into a wall.
A displaced, shaped block at Cuzco. Shows how the block is shaped on all faces.
The blocks were fitted together, and then often joined with lead or silver, which was poured in a molten state into the grooves.
Recovering the silver was possibly one of the reasons why the Spaniards demolished many Inca buildings.
Try fitting a razor blade or even a hair into that join.
The attention to detail was at an incredibly high level in the royal buildings.
Apart from the accuracy of the stonework, the architecture shows amazing accuracy.
another groove for molten silver or lead
Note how the block curves around an inside corner
And outside corners. Quite beautiful.
Some blocks weigh several tons
This is apparently a phallic reference in stone. Count the number of faces on the central stone. It is quite famous.
It would seem they managed all this without the use of iron.
I noticed on one photo the lines of the stones appears flat, you would have thought if they had managed that once they would realise the possibilities of using straight line, edges, sides etc and right angles.
But I suspect that straight lines would have been less earthquake resistant, because the straight edges would have been more inclined to slide on each other. The complex edges would have shown more tendency to lock together. Just guessing.