"Saving some for later."--- Thaumonomicon Entry
The Node Preserver research grants you the ability to draw vis from a node continuously and have it stop when a single point of vis for an aspect is left. This helps to prevent the node from permanently losing the aspect that has its vis completely drained.
Warning: This ability does not work when using wands made either with plain wood cores, or with iron or copper caps.
Take note that this ability of leaving a single point of vis behind does not apply to plain wood cores, or with iron or copper caps. In other words, wooden wands, or wands with iron or copper caps will ALWAYS completely drain the vis in the node.
Aspects required for ResearchEdit
You now have better control over the amount of vis you draw from nodes. You will always leave at least one vis of each aspect in the node, unless you are sneaking.
Be warned, this level of control is not possible when using wands crafted from normal wood and iron (or copper).