There is no "Maximum cash", and Customs did not care about the source of the money, but TD Bank, where I've deposited the money to, was very curious...
You declare only the importation of currency or monetary instruments of a value equal to or greater than $10,000 Canadian (or its equivalent in a foreign currency). I did it twice in April. Filled out the form, declared my USD currency, put in previous day Bank Of Canada exchange rate to fill out the value in CAD. The first time customs counted ( two officers counted by hand, machine did not work!) the money and stamped the form. Last week another officer at the same border did not know what to do, just logged my form in their system, generated code, stamped the form and let me proceed.