Table Design

It depends on the use of the table and the materials available.
If you want to build just one table, it makes sense to design it to use materials which are to hand.
The dimemsions of L are less critical if you add some bracing rather than simply have a leg dangling from each corner...what about aesthetics...?

It would also be daft to calculate dimension for L only to find it came out as a non-standard size. Find out what material are readilly available as standard sizes, pick one which seems about right using your experience of materials and by looking at vaguley similar applications, build a prototype and test it.
All this could be done with no calculation whatsoever....it's a table not a lunar module!
Del
(Insufficient information for a good answer makes it sound like homework).

without doubt it is

calculate the load on each leg and then proceed.

BTW

did you mean

(Insufficient information for it to be treated as a good answer question makes it sound like homework).

But seriously, the joint between legs and table top is the weak point and is more significant than the actual leg profile/dimensions.
E.G You could have a nice strong L section leg, this would provide enough leverage such that one could break the top joint by manual force.
It's a bad question, encouraging simplistic bad design, dumb calculation and no thought or understanding of the actual problem.
Del

As much as I hate to give a GA to a cat (only encourages them, ya know), your comment is dead on. I expect most tables could stand fine on a 3/8" dowel if the side forces were constrained.

For the OP, take a handful of soda straws. Cut them to 1" long. bundle them tightly with two strong gumbands (that's a rubber band for you people who don't appreciate good language). You should be able to stand at least a hundred pounds (how many stones is that?) on the straws.That's what wood looks like.

Go to an antique store. Study Queen Anne tables. Then think about your design.