Halve lemons crosswise and remove seeds. Tie seeds in a cheesecloth bag. Quarter each lemon half and thinly slice. Combine with bag of seeds and water in a large heavy pot and let mixture stand, covered, at room temperature 24 hours.
Add sugar to lemon mixture, and bring to a boil over moderate heat. Reduce heat and simmer, uncovered, about 45 minutes. Stir occasionally, skimming off any foam that appears.
Marmalade is ready when until a teaspoon of lemon mixture dropped on a cold plate gels.
Ladle hot marmalade into jars, filling to within ¼ inch of top. Seal jars with lids, and process 15 minutes in a boiling water bath.
Notes
The original recipe calls for adding the sugar after the lemon-water mixture have been boiled for 45 minutes. Boil an additional five minutes, then begin checking if mixture gels on a plate, and proceed with directions.
Both methods work fine; adding the sugar earlier will result in a sweeter marmalade that is darker in color. Adding the sugar later will result in a lighter taste and color.
Recipe by Sprung At Last at https://sprungatlast.com/2015/02/meyer-lemon-marmalade/