Soulleaf Seed

Soulleaf is one of the few ways of direct and stable income of Ancient Essence. It takes approximately an hour to fully grow, and 20 minutes to regrow. This means, even if not taking first grow time into account, you will be getting an average of 0.009 Essence per second, which is a miniscule amount.

If you want to grow it in hydroponics, you will need the best possible fertilizer - Superior Fertilizer, which is very hard to craft, and even harder to automate. Otherwise, more seeds will be consumed than produced. You may want to grow it on ground (or Aeroponic Tubing), re-harvest with Harvester Turrets, and then collect the harvest with Grabbers. This way, no seeds are consumed.

A Duplicator can supply slightly more than 20 Hydro Trays with Superior Fertilizer. Paired with Organic Soup as a Tray Liquid, the yield will approximately be 300 Essence per minute, or 5 Essence per second.

You can also simply extract duplicated fertilizer in a Precursor Data Box which will yield 2.33 Essence per second. A Precursor Mainframe comes close or may even surpass everything above with a crazy rate of 5.66 Essence per second, which might be the best of the simplest ways to generate Essence if you have both Duplicator and a Mainframe.