In ancient times the ternary was the number par excellence, the favourite of philosophers. The ancients venerated it and enshrined it in their mysteries. The Mason and the Scholar can discover curious relationships with this number. It is truly astonishing to know the numerous attributes with which reason, imagination and feeling have invested it. It was the favourite number of Pythagoras, for whom it was the image of perfect harmony. This number finds application in all sciences, but we will only mention what is relevant to the case. Occult philosophy or Metaphysics consists of three worlds: The Elemental World, The Intellectual World and the Celestial World. In the Universe there is Space, Matter and Movement. The attributes of God or of nature are: Eternity, Infinity and Omnipotence. Nature is divided into three Kingdoms: The Mineral, the Vegetable and the Animal. Each of these is triple, although together they are only one (A Trinity). Time is divided into Past, Present and Future. Man has three intellectual powers: Memory, Understanding and Will. It consists of Body, Soul and Spirit. Bodies have three dimensions, namely Length, Width and Depth. They have shapes, density and colour. As Physics believes that water is condensed air, it only admits three elements: Earth, Fire and Air. Chemistry finds three palpable principles in bodies: Earth, Water and Salt. And to finish the first part of this work. The ancients said that Salt, Sulphur and Mercury were the three chemical principles that animated the Universe.