The sonnet’s opening lines draw from the language of the marriage ceremony in the Book of Common Prayer, which discusses the “union of true minds” as well as the declaration of “any impediment why they may not be coupled together.” The speaker’s use of this language gives the opening quatrain a legalese tone.
“Height be taken” refers to a navigation tool in which seafarers would measure the height of the pole-star and calculate their latitude. This allusion read in conjunction with “whose worth’s unknown” suggests a distinction between physical and figurative measurements: while the height of the star can be calculated, its actual distance is boundless. The star is therefore metaphorically beyond worth, beyond calculation; it exists outside physical systems that could give it a relative value.
