C1 wormholes have a total mass of 1 billion kg. Because any individual wormhole can vary from the average by up to 10%, that means the total mass can be anywhere between 0.9 billion kg and 1.1 billion kg.
With a 20 million kg mass restriction, closing a fresh C1 takes anywhere from 45 to 55 jumps. Taking polarization into account, that means spending roughly two hours jumping back and forth to close a C1 wormhole solo.
In practice, you can do it in about 8-10 jumps, with the right setup. That takes about 20 minutes. The trick is the difference in when the mass restriction is checked, and when the mass jumped is checked.
Obviously, the mass restriction is checked before you even enter the wormhole. This makes sense, as the entire point of the restriction is to prevent large ships from entering the wormhole! However, the mass jumped is checked when you come out the other side. So if your mass changes while transiting the wormhole, you can use up a larger amount of mass than you might think looking at the mass restriction.
The easiest way to increase your mass mid-jump, of course, is to turn on your prop mod. A 50mn prop mod increases your mass by 50 million kg. If you have a Higgs Anchor on your ship, that effect is doubled to 100 million kg, or 10% of the total mass of the wormhole.
In my view, the ideal ship for rolling C1 wormholes is the Gnosis. There are two reasons for this. First, the unaltered mass of the Gnosis is 10 million kg, which means that it comes in at 20 million kg after adding the Higgs Anchor, which is exactly the mass limit of a C1 wormhole.
Second, the Gnosis has amazing agility. With two Nanofiber Internal Structure II, it has less than a 3 second align time. At some point the numbers will go wrong, and you will get rolled out of your wormhole. That align time means you have a real shot at getting your Gnosis to high sec. Throw on some warp stabs and a decent shield tank, and it will take more than a chance engagement on a gate to prevent you reaching safety.