Is a wealth tax constitutional? Keep in mind that they had to pass a constitutional amendment (16th) to get the income tax. The text of that amendment is plain:
"The Congress shall have power to lay and collect taxes on incomes, from whatever source derived, without apportionment among the several States, and without regard to any census or enumeration."
Incomes, not wealth. The apportionment bit is important, because the constitution requires "No Capitation, or other direct, Tax shall be laid, unless in Proportion to the Census or enumeration herein before directed to be taken." So for example, if New York has, say twice the population of New Jersey, New York would pay twice as much of any tax. Obviously this is unworkable with an income tax or a wealth tax.