Where is the source material that reads there is not limit to the number of artifacts a character may have?

I have read elsewhere for Numenera and the Cypher System as a whole, that there are no limits on the number of artifacts a character may possess. However, I have both the Discovery and Cypher System rulebooks and have yet to identify the source for this rule. Does anyone know where this rule comes from? Also, without limits, how does a GM know how to balance access to artifacts with Tier level?