This text comes from The Book of Scottish Song, edited by Alexander Whitelaw, a historical songbook transcribed on Wikisource and reproduced from the pinned revision linked below.
I would I were the light fern growing
Beneath my Highland Mary's tread,
I would I were the green tree throwing
Its shadow o'er her gentle head!
I would I were a wild flower springing
Where my sweet Mary loves to rest,
That she might pluck me while she's singing,
And place me on her snowy breast!
I would I were in yonder heaven
A silver star, whose soft dim light
Would rise to bless each summer even,
And watch my Mary all the night!
I would, beneath these small white fingers,
I were the lute her breath has fanned—
The gentle lute, whose soft note lingers,
As loth to leave her fairy band!
Ah, happy things! ye may not wander
From Scotland to some darker sky,
But ever live unchanging yonder,
To happiness and Mary nigh!
While I at midnight sadly weeping
Upon its deep transparent blue,
Can only gaze while all are sleeping,
And dream my Mary watches too!