How does one use Resources.getFraction()?

How do I store a fractional value like 3.1416 in resources? What to write in the XML and how to retrieve it in Java code?

The documentation for getFraction() states:

public float getFraction (int id, int base, int pbase)

Retrieve a fractional unit for a particular resource ID.

Parameters
base The base value of this fraction. In other words, a standard fraction is multiplied by this value.
pbase The parent base value of this fraction. In other words, a parent fraction (nn%p) is multiplied by this value.

Returns
Attribute fractional value multiplied by the appropriate base value

This answer shows a simple example of percentages without going into the details of what the arguments mean.