Her is the verse from Go.*háuhins mêla (ON Hávamó,l) which I
recently posted to Norse Course:

juggs was ik faúrþis
fôr ik áins samana
warþ ik þan wilþeis wigê
áudags þûhta mis (+ik/ik wisan)
þanei ik anþarana fanþ
manna ist mans gaman

As not everyone reads Gothic, it is pronounced:

jungs was ik forþis
fôr ik ains samana
warþ ik þan wilþîs wigæ'
auðags þûhta mis (ik/ik wisan)
þanî ik anþarana fanþ
manna ist mans gaman

In Old Norse (1st Grammarian's spelling):

ungr vas ek forþum
fór ek einn saman
þá varþ ek villr vega
auþigr þóttumsk
es ek annan fann
maþr es manns gaman

In Proto-Norse (my back-translation):

jungaz was ek fora þaim
fôr ek ainaz samanô
warþ ek þan wilþijaz wegô
audagaz þûhtê mez (ek/ek wesan)
þanî ek anþaranô fanþ
mannaz ist mannas gamana

ON meters like ljóðaháttr and fornyrðislag were inherited from Proto-
Germanic. As the language gradually changed, so did inherited verses
and later speakers' perception of how many syllables a normal line
of verse consisted of. Thus, a younger generation would have known
and understood their parents' version of a verse, even if their own
had one or two less syllables in certain places. This is because the
younger generation adopting a change is still aware of the forms of
the older generation, which has nt adopted the change, or only to a
lesser degree. And he ball rolls on and on. It is only after many
generations that speakers begin having difficulty understanding the
language of an earlier stage, which is then considered dead, as it
no longer has any native speakers. Meters like fornyrðislag and
ljóðaháttr, being based on stress and alliteration rather than any
fixed syllable count, show variation in line-length. Whether a line
is 'correct' or not in terms of its length is a judgement by actual
speakers about what 'feels' natural to them, based on their earlier
experience of the meter in question. This concept of 'feel' is very
important for our understanding of inherited meters showing no fixed
metrical count. It is also important to realize that, as a language
loosed syllables and changes, so does its speakers idea and 'feel'
about what constitutes a normal/natural line.

-K