I avsnittet SRD på Arcane Spells :
Rest
To prepare her daily spells, a wizard must first sleep for 8 hours. The wizard does not have to slumber for every minute of the time, but she must refrain from movement, combat, spellcasting, skill use, conversation, or any other fairly demanding physical or mental task during the rest period. If her rest is interrupted, each interruption adds 1 hour to the total amount of time she has to rest in order to clear her mind, and she must have at least 1 hour of uninterrupted rest immediately prior to preparing her spells. If the character does not need to sleep for some reason, she still must have 8 hours of restful calm before preparing any spells.
(betona min)
SRD nämner inte elvenas förmåga att klara sig på fyra timmars sömn, men som jag minns min förmåga inte min elf behövde vila; Det var bara tillåtet för dem att vara medvetna under en del av tiden.
Jag skulle säga att det gäller här: Elven behöver fortfarande åtta timmar av "vilsam lugn" innan du förbereder dagliga stavar, men kan vara medveten under en del av den tiden.
Divine Spells är mycket enklare:
Time of Day
A divine spellcaster chooses and prepares spells ahead of time, just as a wizard does. However, a divine spellcaster does not require a period of rest to prepare spells. Instead, the character chooses a particular part of the day to pray and receive spells. The time is usually associated with some daily event. If some event prevents a character from praying at the proper time, he must do so as soon as possible. If the character does not stop to pray for spells at the first opportunity, he must wait until the next day to prepare spells.
Efter viloperioden / vid den specifika tidpunkten krävs en timme för att förbereda stavar. Det finns några nyanser till det (trollkarlar kan lämna slots tomma, till exempel) men SRD gör ett bra jobb att täcka reglerna tydligt.