johnsmachines

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.