I usually don't write up this kind of stuff, but I like this formula and don't want to forget. I saw some meyer lemons the other day and couldn't believe how soft their skin was, I grabbed a couple. I chopped them up removing only the central-most membrane and white stuff. The rest, skin, pith and all was finely diced (I chopped up 2 lemons). The lemons (128 g), sugar (128 g) and about 500-700 mL water placed in a sauce pan to barely simmer until it glopped like a lava swamp (about 2 hours). Then I poured it in a jar. It's pretty awesome.
So equal weight sugar and citrus (I've done an orange before using this as well) and enough water, replenishing if necessary, to allow a 2-3 hour gradual simmer/concentration and marmalade.