There are two chambers, so they each get their own working space. Projection is typically better than purification for maintainable machines, but Purification allows near-total separation and economizes out an arm that would be expected to move quicksilver through the 
conduits--so we use that. Keep things simple. Keep things obvious. It is the way of Sum. To build a yin-yang machine, one may consider the full symbol and the inseparable integration of the two when outlining a harmonious many-step process, but I prefer steps of 1) build the yin and 2) build the yang. You can build the yang first if that saves a few cycles, maybe.

- Alchemist Kazyan