Write

By means of this spell a magic-user might be able to inscribe a spell he or she cannot understand at the time (due to level or lack of sufficient Intelligence) into the tome or other compilation he or she employs to maintain a library of spells. 

The magic-user must make a saving throw versus magic to attempt the writing of any spell, +2 if it is only up to 1 level greater than he or she currently uses, 0 at 2 levels higher, and -1 per level from 3 levels higher onwards. If this throw fails, the magic user is subject to 1d4 of damage for every level of the spell he or she was attempting to transcribe into his or her magic book, and furthermore be knocked unconscious for a like number of turns: This damage, if not fatal, can only be healed at the rate of 1-4 points per day, as it is damage to psyche and body. 

Furthermore, a spell will take 1 hour per level to transcribe in this fashion, and during this period, the magic-user is in a trance state and can always be surprised by any foe. 

In addition to the writing surface upon which the spell is to be transcribed, the spell caster needs a fine ink composed of rare substances (minimum cost 200 g.p. per bottle, if available at all without manufacture by the magic-user).

Ink for use with this spell is only 10% likely to be located at any given apothecary/alchemist in a town, or double that for a city. Ink will come in a flask which will be sufficient to inscribe 2-4 spells. The cost will be 200 to 500 gold pieces. You should devise whatever formula for manufacture of this substance you desire. Ichor of slithering tracker, octopus ink, and powdered gems are a fair place to start from.