Something not being externally falsifiable does not necessarily mean it is false.

What does  'falsifiable' and 'measurable' mean with regards to certain domains of the metaphysical or transcendent, which can often be experienced as immeasurable, infinite and eternal?

Measurable refers to material physical substance and processes and the scientific method such as a chemical extraction. The experiences triggered by chemistry in conjunction with one's neurophysiology may not be measurable or externally falsifiable, yet they certainly are internally verifiable each one for themselves.

Indeed, especially with matters that go beyond the scope and purview of the material sciences and into the realm of human subjectivity and its potentials.