Ability Breakdown & Details

When you issue the /meditate command, it initiates a 'You sit down' system message then takes a meditation pose. 
Here's what mediation skill can do for each level of meditation. 
Note that each additional level increases the speed of the previous levels heals.

Teräs Käsi Novice: cure bleeding
Intermediate Meditative Techniques: cure bleeding + cure poison
Advanced Meditative Techniques: cure bleeding + cure poison + cure disease
Expert Meditative Techniques: cure bleeding + cure poison + cure disease (nothing new)
Master Meditative Techniques:= cure bleeding + cure poison + cure disease + cure wounds

In addition, Meditate will make your HAM regenerate faster than standing. 
I'm unsure if it is faster than sitting (although it is at least as fast).

When you meditate you will see something like the following (exact wording may be off):

Your disease severity has decreased.
Your disease severity has decreased.
Your disease severity has decreased.
Your disease has subsided.
[meditation] Your action wounds heal by [31] points.
[meditation] Your action wounds heal by [23] points
[meditation] Your action wounds heal by [15] points.

Each message tends to have aperiod of about 3 or 4 seconds in between.
 So it does heal rather quickly. As for how long specifically it takes 
to heal disease and such, it depends on the severity. For example, 
Mantigrue Screechers on Endor can give some pretty nasty disease that 
hits for upwards of 300 or 400 wounds per tick. That disease usually
takes about 3 or 4 messages to cure while I meditate (so about 12 
seconds more or less). Of course when you get a disease or poison, 
it's usually in your advantage to finish the battle as quickly as 
possible so as to minimize wounding and the time it takes to mediate
 those wounds away. The numbers (for action) I listed above are 
typical heal rates. Each tick tends to heal between 20 and 35 
wounds of one type. And, wounds will never heal while you are 
poisoned or diseased. Meditation always targets the poison or 
disease first. Last thing of note: you can not mediate while 
you have a state applied to you (dizzy, blind, etc.). The only 
things that Meditation won't heal are those types of negative 
states and battle fatigue. Meditation WILL heal all primary and
wounds.

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