Ownership marks and mottos
The thing I wish for is not mortal.....
Non est mortale, quod opto
Lond. 24. March 1631'
Possibly taken from Munde immunde vale, Non est mortale quod opto, Sidera sublimi vertice summa petam.
Meaning: Take wing, my Soule, and mount up higher, For Earth fulfills not my Desire.
The literal meaning is Farewell, foul world, the thing I wish for is not mortal [i.e., I want something better]. I shall aim for the highest stars at the lofty pole.
David Powell, the library’s Greek and Latin scholar, after failing to find the source of the motto has suggested that it doesn’t seem to be from a classical author, though it might be from a Renaissance Latinist, such as an alchemist or the author of an emblem book. It is also not clear whether the first and second lines of the couplet originally belonged together, though they do make good sense in combination. The phrase can bear an elevated meaning (I have set my mind on higher things), though from an alchemist it is more worldly, and from Ganymede (who is shown in an emblem being carried off by Jupiter) equally so: “I want to be taken away from all this by a rich admirer”.
Henricus Bourgehier is a name extending back from the seventeenth century into the middle ages. The inscription is much more likely to be that of Henry Bourchier (c 1587-1654) the 5th Earl of Bath. Having compared the handwriting found in other volumes inscribed by him this seems certain. See the volume held at Cambridge University Library. Bourchier’s Library was sold off after his death by Lionel Cranfield who had married Bourchier’s widow, Lady Rachel Fane. (Oxford Dictionary of National Biography)