Welcome to the first in an ongoing series we're calling "Reference Points." In this series, we will be working backwards in a way, to tell all you lovers of horology about some important watches that we feel make up the foundation of modern wristwatches. We've tried to give you tidbits of historical knowledge in several of our articles over the years – in particular those from the "Historical Perspectives" category – but now we're going even further. For our first "Reference Points" feature, we're starting with what is arguably the most important pairing of complications there is – perpetual calendar chronographs by Patek Philippe. And we're taking you all the way back to the beginning.