Sending an item as lettermail is the cheapest option, though it doesn't include any insurance or tracking by default. To get delivery confirmation, you need to send your item as "Registered Mail", which costs $7.25 for within Canada, or $12.50 for international destinations. That's on top of the lettermail postage price. Sending it as a small parcel might be cheaper because then tracking is included in the price.
|Up to 30g||$0.52||$0.96||$1.60|
|30g - 50g||$0.96||$1.15||$2.30|
|Up to 100g||$1.15||$1.92||$3.75|
|100g - 200g||$1.92||$3.20||$6.40|
|200g - 500g||$2.65||$6.40||$12.80|
*Note that for USA/INTL, the max width is listed as 150mm.
For all the fine print, see the Canada Post Guide to Lettermail.
They have one page, which is not easy to find, that has a very nice PDF with all the relevant information in one place: Canada Post Prices. Or, you can see a list of all the PDFs. I recommend the main "Canada Post Prices" one.
My next step is scanning through these docs to make a handy reference table for the small/light packet rates.