That's what I do for my password manager password. I use German capitalization rules (all nouns are capitalized, not just proper nouns) and numeric and special characters where appropriate. Then I have a particular obscure quote which I remember in slightly misquoted form.
For example (NOT the one I really use of course!) "Four Score and Seven Years ago, some Mothers brought forth upon this Continent a new Nation" would be "4S&7Ya,sMb4thutCanN"